Three-dimensional measurement device

ABSTRACT

A three-dimensional measurement device includes: an irradiator that emits a predetermined light; an optical system that splits the predetermined light into two lights, irradiates a measurement object with a measurement light and irradiates a reference plane with a reference light, and emits a combined light; an imaging device that takes an image of the combined light and obtains an interference fringe image; an objective lens for the measurement light that directs the measurement light toward the measurement object; an objective lens for the reference light that directs the reference light toward the reference plane; an imaging lens that forms an image of the combined light on the imaging device; and a control device that executes three-dimensional measurement of a measurement area on the measurement object based on the interference fringe image.

BACKGROUND Technical Field

The present disclosure relates to a three-dimensional measurement deviceconfigured to measure the shape of an object to be measured or ameasurement object.

Description of Related Art

One conventionally known three-dimensional measurement device configuredto measure the shape of a measurement object is, for example, aninterference-type three-dimensional measurement device that takesadvantage of the technique of digital holography to perform heightmeasurement of bumps of a semiconductor wafer (refer to, for example,Patent Literature 1).

This type of three-dimensional measurement device enables heightmeasurement of a bump exceeding a measurement range to be performed byone-shot imaging without requiring a moving mechanism of a referenceplane, a galvanic mechanism or the like.

PATENT LITERATURE

-   Patent Literature 1: JP 2019-100961A

In three-dimensional measurement using the technique of digitalholography, it is required to specify a reconstructed image in afocusing state among a plurality of reconstructed images (intensityimage data reconstructed with regard to a plurality of positions in aheight direction). Accordingly, it is important to detect the luminanceof a measurement point.

In the configuration described in Patent Literature 1, however, there isno significant difference between luminances of the plurality ofreconstructed images. This makes it difficult to specify whichreconstruction position is a focusing position (or an optimum focusingposition where an image is most focused in the height direction). As aresult, this is likely to reduce the measurement accuracy.

Especially, when part of the measurement object is curved like the bumpdescribed above, the light which the curved portion is irradiated withis diffused. This reduces the amount of the reflected light to bedetected and is thus likely to make the phenomenon described above morenoticeable.

SUMMARY

One or more embodiments of the present disclosure provide athree-dimensional measurement device that improves the measurementaccuracy and enhances the measurement efficiency.

The following describes each of various aspects provided adequately inview of above issues. Functions and advantageous effects that arecharacteristic of each of the aspects are also described as appropriate.

Aspect 1. There is provided a three-dimensional measurement device,comprising: a predetermined optical system (a specific optical system)configured to split a predetermined light entering therein into twolights, to irradiate a measurement object (for example, a wafersubstrate) with one of the two lights as a measurement light andirradiate a reference plane with the other of the two lights as areference light, and to combine the measurement light and the referencelight with each other and emit a combined light; an irradiation unit (orirradiator) configured to emit the predetermined light that enters thepredetermined optical system; an imaging unit (or imaging device)configured to take an image of an output light (combined light) emittedfrom the predetermined optical system and obtains an interference fringeimage; an objective lens for the measurement light configured to directand radiate the measurement light toward the measurement object; anobjective lens for the reference light configured to direct and radiatethe reference light toward the reference plane; an imaging lensconfigured to form an image of the output light (combined light) ontothe imaging unit (an imaging element of the imaging unit); and an imageprocessing unit (or control device) configured to perform (execute)three-dimensional measurement with regard to (of) a predeterminedmeasurement area of (on) the measurement object (the entirety or part ofthe measurement object), based on an interference fringe image(hologram) obtained by imaging by the imaging unit. The image processingunit comprises: an image data obtaining unit configured to obtain, byreconstruction, intensity image data at a predetermined position in adirection of (along) an optical axis with regard to (for) eachcoordinate position (each coordinate) in the measurement area, based onthe interference fringe image with regard to (of) the measurement areaobtained by imaging by the imaging unit; a phase information obtainingunit configured to obtain, by reconstruction, phase information of lightat the predetermined position in the direction of (along) the opticalaxis with regard to (for) each coordinate position (each coordinate) inthe measurement area, based on the interference fringe image with regardto (of) the measurement area obtained by imaging by the imaging unit; afocusing determination unit configured to determine whether theintensity image data is in a focusing state that satisfies apredetermined condition (for example, the intensity image data has aluminance of not lower than a predetermined reference value), based onthe intensity image data at the predetermined position in the directionof (along) the optical axis with regard to (with respect to) apredetermined coordinate position (predetermined coordinate) in themeasurement area obtained by the image data obtaining unit; an orderspecification unit configured to, after determining that the intensityimage data at the predetermined position in the direction of (along) theoptical axis is in the focusing state with regard to the predeterminedcoordinate position, based on a result of determination by the focusingdetermination unit, specify an order corresponding to the predeterminedposition in the direction of (along) the optical axis, among ordersdetermined (set) at a predetermined measurement range interval in thedirection of (along) the optical axis, as an order with regard to (of)the predetermined coordinate position; and a three-dimensionalmeasurement unit configured to perform (execute) three-dimensionalmeasurement (height measurement) with regard to the predeterminedcoordinate position (predetermined coordinate), based on the phaseinformation with regard to (of) the predetermined coordinate positionobtained by the phase information obtaining unit and the order withregard to (of) the predetermined coordinate position specified by theorder specification unit.

The “predetermined optical system” includes not only an “optical systemthat causes the reference light and the measurement light to interferewith each other inside thereof and outputs these two lights asinterfering light” but “an optical system that outputs the referencelight and the measurement light simply as a combined light withoutinterfering with each other inside thereof.” When the “output light”output from the “predetermined optical system” is “combined light”,however, the combined light is to be converted into “interfering light”via a predetermined interference element in at least a previous stageprior to imaging by the “imaging unit”.

An optical system configured to split a predetermined incident lightinto two lights, to irradiate a measurement object with one of the twolights as a measurement light and irradiate a reference plane with theother of the two lights as a reference light, recombine the measurementlight and the reference light with each other, and emit the recombinedlight for the purpose of making interference of light (takinginterference fringe images) may thus be referred to as an “interferenceoptical system”. Accordingly, in Aspect 1 described above (and otheraspects described later), the “predetermined optical system (specificoptical system)” may be called the “interference optical system”.

The configuration of above Aspect 1 using the technique of digitalholography allows for height measurement exceeding the measurement rangewith regard to each of the coordinate positions in the measurement area.This configuration is simplified without requiring any large-scaledmoving mechanism such as to move the measurement object and is notaffected by the vibration or the like of the moving mechanism, andaccordingly achieves the improvement of the measurement accuracy.

Furthermore, the configuration of above Aspect 1 enables all theinterference fringe images required for measurement to be obtained bythe less number of times of imaging and thereby enhances the measurementefficiency.

Additionally, the configuration of above Aspect 1 is provided with theobjective lens for the measurement light, the objective lens for thereference light and the imaging lens configured to form an image of theoutput light on the imaging unit and thereby further improves themeasurement accuracy.

The following describes the functions and the advantageous effects ofthe characteristics of Aspect 1 provided with the objective lenses andthe imaging lens. FIG. 16 is a diagram illustrating an opticalrelationship between an objective lens and an imaging lens relating toAspect 1 and schematically illustrates an optical system that causes animage of a measurement object 700 to be formed on an imaging unit 703via an objective lens 701 and an imaging lens 702.

As shown in this diagram, a procedure of three-dimensional measurementusing the technique of digital holography reconstructs intensity imagedata at a plurality of positions z₁ to z_(n) in a direction of anoptical axis J1 (in a direction of a height z) and specifies areconstructed image at a focusing position z_(p) where an image isfocused in the direction of the optical axis J1 (or at an optimumfocusing position z_(p) where an image is most focused in the directionof the optical axis J1) among a plurality of these intensity image data(reconstructed images).

It is important to detect the luminance of the measurement point asdescribed above in “Description of Related Art”, in order to specify areconstructed image in a focusing state among a plurality ofreconstructed images.

The following describes the principle of determining whether areconstructed image with regard to a pixel at a predetermined positionis a reconstructed image at a focusing position (or at an optimumfocusing position), based on a luminance of the pixel at thepredetermined position in the reconstructed image.

There is no difference in total amount of luminance between areconstructed image at a focusing position and a reconstructed image ata position other than the focusing position. Even in the case wherelight is concentrated or blurred in an identical pixel (one pixel at anidentical position in an x-y coordinate system), no change in theluminance (total amount of luminance) appears in the pixel.

For example, in the case of imaging a small measurement point PA, it isassumed that the measurement point PA is at the center of apredetermined pixel 800 a in a reconstructed image 800 at a focusingposition as shown in FIG. 17A. Even in the case where the measurementpoint PA is blurred to a size of 0.5 pixels in each of the x directionand the y direction (half the length of each side of a pixel 801 a) in areconstructed image 801 at a position shifted from the focusing positionby a first predetermined amount in the direction of the optical axis (inthe direction of the height z) as shown in FIG. 17B, a deviation fromthe focusing position is not determinable since there is no change inthe luminance (the total amount of luminance) in the pixel 801 aincluding the measurement point PA.

In the case where the measurement point PA is blurred beyond the size of0.5 pixels in each of the x direction and the y direction (half thelength of each side of a pixel 802 a) in a reconstructed image 802 at aposition shifted from the focusing position by a second predeterminedamount in the direction of the optical axis (in the direction of theheight z) as shown in FIG. 17C, on the other hand, the luminance (thetotal amount of luminance) decreases in the pixel 802 a including themeasurement point PA. A deviation from the focusing position is thusdeterminable by detecting this change. In other words, the luminanceincreases in pixels around the pixel 802 a including the measurementpoint PA. A deviation from the focusing position is also determinable bydetecting this change.

In another example, in the case of imaging a small measurement point PA,it is assumed that the measurement point PA is over four pixels 800 a ina reconstructed image 800 at a focusing position as shown in FIG. 18A.Even in the case where the measurement point PA is blurred to a size ofone pixel in each of the x direction and the y direction (the length ofeach side of a pixel 801 a) in a reconstructed image 801 at a positionshifted from the focusing position by a first predetermined amount inthe direction of the optical axis (in the direction of the height z) asshown in FIG. 18B, a deviation from the focusing position is notdeterminable since there is no change in the luminance (the total amountof luminance) in each of the four pixels 801 a including the measurementpoint PA.

In the case where the measurement point PA is blurred beyond the size ofone pixel in each of the x direction and the y direction (the length ofeach side of a pixel 802 a) in a reconstructed image 802 at a positionshifted from the focusing position by a second predetermined amount inthe direction of the optical axis (in the direction of the height z) asshown in FIG. 18C, on the other hand, the luminance (the total amount ofluminance) decreases in each of the four pixel 802 a including themeasurement point PA. A deviation from the focusing position is thusdeterminable by detecting this change. In other words, the luminanceincreases in pixels around the four pixels 802 a including themeasurement point PA. A deviation from the focusing position is alsodeterminable by detecting this change.

In the actual state, however, as shown in FIG. 19 , in the case where areconstruction position PS is shifted by a predetermined amount dz froma focusing position PO in the direction of the optical axis (in thedirection of the height z), the measurement point PA is blurred to acircular shape having a diameter of 8. An increase in the relativedistance dz from the focusing position PO increases the degree ofblurring of the measurement point PA (reconstruction state) in areconstructed image at the reconstruction position PS.

Furthermore, using the object lens 900 and the like as shown in FIG. 19increases the degree of blurring of the measurement point PA even at anidentical reconstruction position PS having an identical relativedistance dz from a focusing position PO, compared with a conventionalconfiguration without using the object lens 900 and the like (refer to aportion of two-dot chain line in FIG. 19 ).

The following describes the functions and the advantageous effects ofthe present disclosure (Aspect 1) with comparison between luminancevalues with regard to a predetermined measurement point in a pluralityof reconstructed images obtained under a “conventional” configurationwithout object lenses and the like and luminance values with regard to apredetermined measurement point in a plurality of reconstructed imagesobtained under the configuration of the “present disclosure (Aspect 1)”with the object lenses and the like.

FIG. 21 is a table illustrating luminance values at a predeterminedmeasurement point in a plurality of reconstructed images that arereconstructed at height positions set at reconstruction intervals of “30μm” in the direction of the optical axis (in the direction of the heightz), more concretely, at height positions of “3^(rd) (+90 μm)”, “2nd (+60μm)”, “1^(st) (+30 μm)”, “0^(th) (0 μm)”, “−1^(st) (−30 μm)”, “−2nd (−60μm)”, and “−3^(rd) (−90 μm)”, under the “conventional” configuration andunder the configuration of the “present disclosure (Aspect 1)”.

As shown in FIG. 21 , in the “conventional” configuration, the luminancevalue with regard to the predetermined measurement point in thereconstructed image reconstructed at the height position of “0^(th) (0μm)” is “128” that is a maximum value. The luminance values with regardto the predetermined measurement point in the reconstructed imagesreconstructed at the height position of “1^(st) (+30 μm)” and at theheight position of “−1^(st) (−30 μm)” are respectively “120”. Theluminance values with regard to the predetermined measurement point inthe reconstructed images reconstructed at the height position of “2^(nd)(+60 μm)” and at the height position of “−2^(nd) (−60 μm)” arerespectively “112”. The luminance values with regard to thepredetermined measurement point in the reconstructed imagesreconstructed at the height position of “3^(rd) (+90 μm)” and at theheight position of “−3^(rd) (−90 μm)” are respectively “104”.

Based on these data, in the case illustrated in FIG. 21 , the heightposition of “0^(th) (0 μm)” is specified as the focusing position in the“conventional” configuration.

In the configuration of the “present disclosure”, on the other hand, theluminance value with regard to the predetermined measurement point inthe reconstructed image reconstructed at the height position of “0^(th)(0 μm)” is “128” that is a maximum value. The luminance values withregard to the predetermined measurement point in the reconstructedimages reconstructed at the height position of “1^(st) (+30 μm)” and atthe height position of “−1^(st) (−30 μm)” are respectively “100”. Theluminance values with regard to the predetermined measurement point inthe reconstructed images reconstructed at the height position of “2^(nd)(+60 μm)” and at the height position of “−2^(nd) (−60 μm)” arerespectively “72”. The luminance values with regard to the predeterminedmeasurement point in the reconstructed images reconstructed at theheight position of “3^(rd) (+90 μm)” and at the height position of“−3^(rd) (−90 μm)” are respectively “44”.

Based on these data, in the case illustrated in FIG. 21 , the heightposition of “0^(th) (0 μm)” is specified as the focusing position in theconfiguration of the “present disclosure”.

In the “conventional” configuration described above, the luminancevalues with regard to the predetermined measurement point in thereconstructed images reconstructed at the height position of “±1^(st)(±30 μm)” are respectively “120”, while the peak luminance value withregard to the predetermined measurement point in the reconstructed imagereconstructed at the height position of “0^(th) (0 μm)” is “128”. Aluminance difference from the peak is “8”. Similarly, the luminancevalues with regard to the predetermined measurement point in thereconstructed images reconstructed at the height position of “±2^(nd)(±60 μm)” are respectively “112”, and a luminance difference from thepeak is “16”. The luminance values with regard to the predeterminedmeasurement point in the reconstructed images reconstructed at theheight position of “±3^(rd) (±90 μm)” are respectively “104”, and aluminance difference from the peak is “24”.

In the configuration of the “present disclosure”, on the other hand, theluminance values with regard to the predetermined measurement point inthe reconstructed images reconstructed at the height position of “1^(st)(±30 μm)” are respectively “100”, while the peak luminance value withregard to the predetermined measurement point in the reconstructed imagereconstructed at the height position of “0^(th) (0 μm)” is “128”. Aluminance difference from the peak is “28”. Similarly, the luminancevalues with regard to the predetermined measurement point in thereconstructed images reconstructed at the height position of “±2^(nd)(±60 μm)” are respectively “72”, and a luminance difference from thepeak is “56”. The luminance values with regard to the predeterminedmeasurement point in the reconstructed images reconstructed at theheight position of “±3^(rd) (±90 μm)” are respectively “44”, and aluminance difference from the peak is “84”.

The configuration of the “present disclosure (Aspect 1)” using theobjective lenses and the like has a greater change in the luminancevalue of the measurement point at the reconstruction position having theidentical relative distance (reconstruction distance) from the focusingposition, compared with the “conventional” configuration without usingthe objective lenses and the like. This makes it easier to specify thefocusing position and is less likely to be affected by the noise and thelike. As a result, this configuration improves the measurement accuracy.

Aspect 2. There is provided a three-dimensional measurement device,comprising: a predetermined optical system (a specific optical system)configured to split a predetermined light entering therein into twolights, to irradiate a measurement object (for example, a wafersubstrate) with one of the two lights as a measurement light andirradiate a reference plane with the other of the two lights as areference light, and to combine the measurement light and the referencelight with each other and emit a combined light; an irradiation unit (orirradiator) configured to emit the predetermined light that enters thepredetermined optical system; an imaging unit (or imaging device)configured to take an image of an output light (combined light) emittedfrom the predetermined optical system and obtains an interference fringeimage; an objective lens for the measurement light configured to directand radiate the measurement light toward the measurement object; anobjective lens for the reference light configured to direct and radiatethe reference light toward the reference plane; an imaging lensconfigured to form an image of the output light (combined light) ontothe imaging unit (an imaging element of the imaging unit); and an imageprocessing unit (or control device) configured to perform (execute)three-dimensional measurement with regard to (of) a predeterminedmeasurement area of (on) the measurement object (the entirety or part ofthe measurement object), based on the interference fringe image(hologram) obtained by imaging by the imaging unit. The image processingunit comprises: an image data obtaining unit configured to obtain, byreconstruction, a plurality of (pieces of) intensity image data at apredetermined interval at least within a predetermined range in adirection of (along) an optical axis, each (piece of) intensity imagedata being at a predetermined position in the direction of (along) theoptical axis with regard to (for) each coordinate position (eachcoordinate) in the measurement area, based on the interference fringeimage with regard to (of) the measurement area obtained by imaging bythe imaging unit; a focusing position determination unit configured todetermine a predetermined focusing position in the direction of (along)the optical axis (for example, a position in the direction of theoptical axis where most-focused intensity image data is obtained) withregard to (for) a predetermined coordinate position (predeterminedcoordinate) in the measurement area, based on the plurality of intensityimage data with regard to (with respect to) the predetermined coordinateposition (predetermined coordinate) in the measurement area obtained bythe image data obtaining unit; an order specification unit configured tospecify an order corresponding to the focusing position in the directionof (along) the optical axis with regard to (for) the predeterminedcoordinate position (predetermined coordinate) determined by thefocusing position determination unit, among orders determined (set) at apredetermined measurement range interval in the direction of (along) theoptical axis, as an order with regard to (of) the predeterminedcoordinate position (predetermined coordinate); a phase informationobtaining unit configured to obtain, by reconstruction, phaseinformation of light at the predetermined position in the direction of(along) the optical axis with regard to (for) each coordinate position(each coordinate) in the measurement area, based on the interferencefringe image with regard to (of) the measurement area obtained byimaging by the imaging unit; and a three-dimensional measurement unitconfigured to perform (execute) three-dimensional measurement (heightmeasurement) with regard to the predetermined coordinate position, basedon the phase information with regard to (of) the predeterminedcoordinate position (predetermined coordinate) obtained by the phaseinformation obtaining unit and the order with regard to (of) thepredetermined coordinate position specified by the order specificationunit.

The configuration of above Aspect 2 has similar functions andadvantageous effects to those of Aspect 1 described above.

Aspect 3. There is provided a three-dimensional measurement device,comprising: a predetermined optical system (a specific optical system)configured to split a predetermined light entering therein into twolights, to irradiate a measurement object (for example, a wafersubstrate) with one of the two lights as a measurement light andirradiate a reference plane with the other of the two lights as areference light, and to combine the measurement light and the referencelight with each other and emit a combined light; an irradiation unit (orirradiator) configured to emit the predetermined light that enters thepredetermined optical system; an imaging unit (or imaging device)configured to take an image of an output light (combined light) emittedfrom the predetermined optical system and obtains an interference fringeimage; an objective lens for the measurement light configured to directand radiate the measurement light toward the measurement object; anobjective lens for the reference light configured to direct and radiatethe reference light toward the reference plane; an imaging lensconfigured to form an image of the output light (combined light) ontothe imaging unit (an imaging element); and an image processing unit (orcontrol device) configured to perform (execute) three-dimensionalmeasurement with regard to (of) a predetermined measurement area of (on)the measurement object (the entirety or part of the measurement object),based on the interference fringe image (hologram) obtained by imaging bythe imaging unit. The image processing unit comprises: a first imagedata obtaining unit configured to obtain, by reconstruction, a pluralityof (pieces of) intensity image data at a predetermined interval at leastwithin a first range in a direction of (along) an optical axis, each(piece of) intensity image data being at a predetermined position in thedirection of (along) the optical axis with regard to (within) a specificarea that is a part set in advance in the measurement area, based on theinterference fringe image obtained by imaging by the imaging unit; afirst focusing position determination unit configured to determine apredetermined (first) focusing position in the direction of (along) theoptical axis with regard to (within) the specific area, based on theplurality of intensity image data with regard to (with respect to) thespecific area obtained by the first image data obtaining unit; a secondimage data obtaining unit configured to obtain, by reconstruction, aplurality of (pieces of) intensity image data at a predeterminedinterval at least within a second range in the direction of (along) theoptical axis, which is set on a basis of the focusing position in thedirection of the optical axis with regard to the specific area, eachpiece of intensity image data being at a predetermined position in thedirection of (along) the optical axis with regard to (for) eachcoordinate position (each coordinate) in the measurement area, based onthe interference fringe image with regard to (of) the measurement areaobtained by imaging by the imaging unit; a second focusing positiondetermination unit configured to determine a predetermined (second)focusing position in the direction of (along) the optical axis withregard to (for) a predetermined coordinate position (predeterminedcoordinate) in the measurement area, based on the plurality of intensityimage data with regard to the predetermined coordinate position in themeasurement area obtained by the second image data obtaining unit; anorder specification unit configured to specify an order corresponding tothe focusing position in the direction of the optical axis with regardto the predetermined coordinate position determined by the secondfocusing position determination unit, among orders determined (set) at apredetermined measurement range interval in the direction of (along) theoptical axis, as an order with regard to (of) the predeterminedcoordinate position; a phase information obtaining unit configured toobtain, by reconstruction, phase information of light at thepredetermined position in the direction of (along) the optical axis withregard to (for) each coordinate position (each coordinate) in themeasurement area, based on the interference fringe image with regard tothe measurement area obtained by imaging by the imaging unit; and athree-dimensional measurement unit configured to perform (execute)three-dimensional measurement (height measurement) with regard to thepredetermined coordinate position (predetermined coordinate), based onthe phase information with regard to (of) the predetermined coordinateposition obtained by the phase information obtaining unit and the orderwith regard to (of) the predetermined coordinate position specified bythe order specification unit.

The configuration of above Aspect 3 has similar functions andadvantageous effects to those of Aspect 1 and Aspect 2 described above.Especially, the configuration of this aspect first obtains the intensityimage data at a plurality of positions in the direction of the opticalaxis not with regard to the entire measurement area but with regard tothe specific area (a limited narrow range) that is a part set in advancein the measurement area, and specifies the position of the measurementobject in the direction of the optical axis, based on the focusing stateof the intensity image data.

The configuration of this aspect subsequently obtains intensity imagedata at a plurality of positions in the direction of the optical axis,with regard to each of the coordinate positions in the entiremeasurement area, on the basis of the focusing position with regard tothe specific area.

This configuration reduces the load of the process of obtaining datarequired for three-dimensional measurement with regard to themeasurement area and shortens the time period required for this process.As a result, the configuration of this aspect improves the measurementaccuracy and enhances the measurement efficiency.

Aspect 4. In the three-dimensional measurement device described in anyof Aspects 1 to 3 described above, the objective lens may have anumerical aperture NA that satisfies an expression given below:

NA>a/√((dz)² +a ²)

where a denotes a pixel size and dz denotes a reconstruction interval.

In the case of using the objective lens having a relatively smallnumerical aperture NA, even a relatively large reconstruction intervaldz (relative distance from the focusing position) is likely to reducethe degree of blurring of a measurement point and makes it difficult tospecify the focusing position.

In the case of using the objective lens having a relatively largenumerical aperture NA like the objective lens of Aspect 4 describedabove, on the other hand, reflected light that is reflected in a widerange from a curved portion of the measurement object, such as a topportion of a bump, is more readily received by the objective lens. Evena small reconstruction interval dz is likely to increase the degree ofblurring of the measurement point and makes it easier to specify thefocusing position. As a result, the configuration of above Aspect 4further enhances the functions and the advantageous effects of Aspect 1and the like described above.

The following describes the functions and the advantageous effects ofthe characteristics of Aspect 4. For example, when a semispherical bump101 is a measurement object (a measurement target) as shown in FIG. 20 ,irradiated light K1 which the periphery of a top of the bump 101 isirradiated with has reflected light K2 that is diffused. In this state,an objective lens 901 having a large numerical aperture NA can receivethe reflected light K2 from the bump 101 in a wider range, compared withan objective lens 902 having a small numerical aperture NA (refer to aportion of a two-dot chain line in FIG. 20 ).

Accordingly, a measurable range G1 by using the objective lens 901having the large numerical aperture NA is larger than a measurable rangeG2 by using the objective lens 902 having the small numerical apertureNA.

As described above, in order to reliably detect whether there is adeviation from the focusing position, as shown in FIGS. 17A and 17C andFIGS. 18A and 18C, the blurring of a predetermined measurement point PAis required to be larger than a size of at least two pixels as a whole.

More concretely, it is required to satisfy a relationship of Expression(1) given below, in order to make the blurring of the measurement pointPA larger than the size of two pixels. In other words, a diameter 8 of acircle formed by blurring of the measurement point PA is required to belarger than double a pixel size a (as shown in FIG. 19 ):

ε>2a  (1)

As shown in FIG. 19 , the numerical aperture NA is expressed byExpression (2) given below, where θ denotes a maximum angle of a lightbeam entering an objective lens 900 from the measurement point PA, to anoptical axis J1, and n denotes a refractive index of a medium betweenthe measurement point PA and the objective lens 900 (n is approximatelyequal to 1 in the air):

NA=n×sin θ  (2)

A relationship of Expression (3) given below is established, where dzdenotes a reconstruction interval (a relative distance from the focusingposition) (as shown in FIG. 19 ):

ε=2×dz×tan θ  (3)

Expression (4) given below is led from Expression (1) and Expression (3)given above:

2×dz×tan θ>2a  (4)

Since tan θ=sin θ/(1−sin² θ), Expression (5) given below is led fromExpression (4) given above:

2×dz×{sin θ/(√1−sin² θ)}>2a  (5)

Expression (6) given below is obtained by substituting Expression (2)given above where the refractive index n=1 into Expression (5) givenabove:

2×dz×{(NA)/√(1−(NA)²}>2a  (6)

Expression (7) given below is obtained by dissolving Expression (6)given above with respect to the numerical aperture NA:

NA>a/√((dz)² +a ²)  (7)

In one or more embodiments, the reconstruction intervals dz is not lessthan 0 and does not exceed the measurement range interval R (0≤dz≤R).The measurement range R is a measurement range of the three-dimensionalmeasurement device. For example, in the case of measurement by usingonly one light of one wavelength, a measurement range determinedaccording to the wavelength corresponds to the measurement range R. Inthe case of measurement by using two lights of two differentwavelengths, a measurement range determined according to a compositewavelength of the two wavelengths corresponds to the measurement rangeR.

The numerical aperture NA may be larger as long as possible in one ormore embodiments. Unless a special technique such as liquid immersion isemployed, however, the upper limit of the numerical aperture NA is equalto 1 (refer to Expression (2) given above in the case of a refractiveindex n=1). Accordingly, the numerical aperture NA is not greater than 1(NA≤1) in one or more embodiments.

Aspect 5. In the three-dimensional measurement device described in anyof Aspects 1 to 4 described above, the irradiation unit may comprise afirst irradiation unit (or first light emitter) configured to emit afirst light that includes a polarized light of a first wavelength andthat enters the predetermined optical system; a second irradiation unit(or second light emitter) configured to emit a second light thatincludes a polarized light of a second wavelength and that enters thepredetermined optical system; a projection lens for the first lightplaced between the predetermined optical system and the firstirradiation unit and configured to collect the first light directed ontothe objective lens; and a projection lens for the second light placedbetween the predetermined optical system and the second irradiation unitand configured to collect the second light directed onto the objectivelens. The imaging unit may include a first imaging unit (or firstimaging device) configured to take an image of an output light (combinedlight) with regard to the first light that is emitted from thepredetermined optical system once the first light enters thepredetermined optical system; and a second imaging unit (or secondimaging device) configured to take an image of an output light (combinedlight) with regard to the second light that is emitted from thepredetermined optical system once the second light enters thepredetermined optical system. The imaging lens may include an imaginglens for first imaging configured to form an image of the output light(combined light) with regard to (of) the first light on the firstimaging unit; and an imaging lens for second imaging configured to forman image of the output light (combined light) with regard to (of) thesecond light on the second imaging unit.

The “first light” emitted from the “first irradiation unit” is a lightincluding at least the “polarized light (first polarized light) of thefirst wavelength” and may be a light including another extra componentthat is subsequently to be cut in the “predetermined optical system”(for example, a “non-polarized light” or a “circularly polarizedlight”).

Similarly, the “second light” emitted from the “second irradiation unit”is a light including at least the “polarized light (second polarizedlight) of the second wavelength” and may be a light including anotherextra component that is subsequently to be cut in the “predeterminedoptical system” (for example, a “non-polarized light” or a “circularlypolarized light”).

The “output light with regard to the first light” output from the“predetermined optical system (the specific optical system) includes a“combined light of the reference light and the measurement light withregard to the first light or an interference light obtained byinterfering the combined light”. The “output light with regard to thesecond light” includes a “combined light of the reference light and themeasurement light with regard to the second light or an interferencelight obtained by interfering the combined light”.

The configuration of above Aspect 5 uses two lights of differentwavelengths to expand the measurement range and is provided with the twoimaging units to enhance the measurement efficiency.

In the configuration including the objective lenses like above Aspect 1or the like, the light radiated to the measurement object is gathered atone point (a narrow range) in the measurement range. This is likely tonarrow the measurement area that is measurable by one measurement.

The configuration including the projection lens to cause the lightemitted from the irradiation unit to be directed to and collected by theobjective lens like above Aspect 5, on the other hand, enables a widerrange of the measurement object to be irradiated with uniform parallellight. As a result, this configuration enables a wider range to bemeasured by one measurement.

Aspect 6: In the three-dimensional measurement device described in anyof Aspects 1 to 5 described above, the measurement object may be a wafersubstrate with a bump formed thereon.

The configuration of above Aspect 6 allows for measurement of the bumpformed on the wafer substrate. This accordingly enables an inspection ofthe bump to be performed to determine the good/poor quality of the bump,based on a measurement value thereof. The functions and the advantageouseffects of the respective aspects described above are applied to thisinspection of the bump and allows for the good/poor quality judgmentwith the high accuracy. As a result, this improves the inspectionaccuracy and enhances the inspection efficiency in a bump inspectiondevice.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating athree-dimensional measurement device;

FIG. 2 is a block diagram illustrating the electrical configuration ofthe three-dimensional measurement device;

FIG. 3 is an optical path diagram illustrating an optical path of firstlight;

FIG. 4 is an optical path diagram illustrating an optical path of secondlight;

FIG. 5 is a flowchart showing the flow of a measurement process;

FIG. 6 is an explanatory diagram illustrating a positional relationshipbetween a work and an imaging element and the like;

FIG. 7 is an explanatory diagram illustrating a positional relationshipbetween the work and the imaging element and the like;

FIG. 8 is a schematic diagram illustrating three-dimensional measurementof a wafer substrate;

FIG. 9 is a schematic diagram illustrating three-dimensional measurementof a bump;

FIG. 10 is a schematic diagram illustrating two-dimensional measurementof bumps;

FIG. 11 is a diagram illustrating a relationship between a measurementrange, a phase, an order, height measurement values and the like by oneconcrete example;

FIG. 12 is a diagram illustrating a relationship between the measurementrange, the phase, the order, the height measurement values and the likeaccording to another example of one or more embodiments;

FIG. 13 is a schematic configuration diagram illustrating a cameraaccording to another example of one or more embodiments;

FIG. 14 is a flowchart showing the flow of a measurement processaccording to another example of one or more embodiments;

FIG. 15 is a schematic configuration diagram illustrating athree-dimensional measurement device according to another example of oneor more embodiments;

FIG. 16 is a diagram illustrating an optical relationship between anobjective lens and an imaging lens;

FIG. 17A is a diagram illustrating a reconstruction state of ameasurement point at a focusing position; FIG. 17B is a diagramillustrating a reconstruction state of a measurement point at a positiondeviated by a first predetermined amount from the focusing position; andFIG. 17C is a diagram illustrating a reconstruction state of ameasurement point at a position deviated by a second predeterminedamount from the focusing position;

FIG. 18A is a diagram illustrating a reconstruction state of ameasurement point at a focusing position; FIG. 18B is a diagramillustrating a reconstruction state of a measurement point at a positiondeviated by a first predetermined amount from the focusing position; andFIG. 18C is a diagram illustrating a reconstruction state of ameasurement point at a position deviated by a second predeterminedamount from the focusing position;

FIG. 19 is a schematic diagram illustrating a correspondencerelationship between a focusing position of a measurement point, arelative distance between the focusing position and a reconstructionposition; a degree of blurring of the measurement point at thereconstruction position (reconstruction state), an angle of incidentlight from the measurement point to an objective lens and the like;

FIG. 20 is a schematic diagram illustrating a difference between ameasurable range in the case of using an objective lens of a largenumerical aperture and a measurable range in the case of using anobjective lens of a small numerical aperture; and

FIG. 21 is a table illustrating luminance values with regard to apredetermined measurement point in a plurality of reconstructed imagesreconstructed at a plurality of height positions under a conventionalconfiguration and a configuration of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the three-dimensional measurementdevice with reference to drawings. The three-dimensional measurementdevice of one or more embodiments is a measurement device configured toperform three-dimensional measurement by using digital holography. The“digital holography” herein means a technique of obtaining aninterference fringe image (hologram) and reconstructing an image fromthe obtained hologram.

FIG. 1 is a schematic diagram illustrating the general configuration ofa three-dimensional measurement device 1 according to one or moreembodiments. FIG. 2 is a block diagram illustrating the electricalconfiguration of the three-dimensional measurement device 1. In thedescription below, for the purpose of convenience, a front-backdirection on a sheet surface of FIG. 1 is called an “X-axis direction”,a vertical direction on the sheet surface is called a “Y-axisdirection”, and a horizontal direction on the sheet surface is called a“Z-axis direction”.

The three-dimensional measurement device 1 is configured on theprinciple of Michelson interferometer and includes two projectionoptical systems 2A and 2B (first projection optical system 2A and secondprojection optical system 2B) serving as irradiation units configured tooutput lights of specific wavelengths; an interference optical system 3configured to receive incident lights respectively emitted from theprojection optical systems 2A and 2B; two imaging systems 4A and 4B(first imaging system 4A and second imaging system 4B) serving asimaging units configured to take images of the light emitted from theinterference optical system 3; and a control device 5 configured toperform various controls, image processing, arithmetic operations, andthe like relating to, for example, the projection optical systems 2A and2B, the interference optical system 3 and the imaging systems 4A and 4B.

The “control device 5” configures the “image processing unit” accordingto one or more embodiments, and the “interference optical system 3”configures the “predetermined optical system (specific optical system”according to one or more embodiments. In the description of one or moreembodiments, an optical system that splits predetermined incident lightinto two split lights (measurement light and reference light), makes anoptical path difference between the two split lights, recombines thesplit lights, and outputs the recombined light for the purpose ofcausing interference of light (taking an interference fringe image) iscalled the “interference optical system”. More specifically, not only anoptical system that causes two lights to interfere with each otherinside thereof and outputs these two lights as interfering light but anoptical system that outputs two lights as combined light withoutinterfering with each other inside thereof is called the “interferenceoptical system”. As described later in one or more embodiments, in thecase where two lights (measurement light and reference light) are outputas combined light from the “interference optical system” withoutinterfering with each other, interfering light is obtained via apredetermined interference unit at least in a previous stage prior toimaging (for example, inside of the imaging system).

The following first describes the configuration of the two projectionoptical systems 2A and 2B (the first projection optical system 2A andthe second projection optical system 2B) in detail. The first projectionoptical system 2A includes, for example, a first light emitter 11A, afirst light isolator 12A and a first non-polarizing beam splitter 13A.The “first light emitter 11A” configures the “first irradiation unit”according to one or more embodiments.

The first light emitter 11A includes, for example, a laser light sourceconfigured to output linearly polarized light having a specificwavelength λ₁, a beam expander configured to expand the linearlypolarized light output from the laser light source and output theexpanded linearly polarized light as parallel light, a polarizing plateconfigured to adjust the intensity, and a half-wave plate configured toadjust the polarizing direction.

According to one or more embodiments under the above configuration,linearly polarized light that is polarized in a direction inclined at anangle of 45 degrees to the X-axis direction and the Y-axis direction asa polarizing direction and that has a wavelength λ₁ (for example,λ₁=1500 nm) is emitted leftward in the Z-axis direction from the firstlight emitter 11A. The “wavelength λ₁” corresponds to the “firstwavelength” according to one or more embodiments. In the descriptionbelow, the light that is emitted from the first light emitter 11A andthat has the wavelength λ₁ is called “first light”.

The first light isolator 12A is an optical element that causes onlylight traveling in one direction (leftward in the Z-axis directionaccording to one or more embodiments) to be transmitted, while blockinglight traveling in an opposite direction (rightward in the Z-axisdirection according to one or more embodiments). This configurationallows for transmission of only the first light emitted from the firstlight emitter 11A and prevents the first light emitter 11A from beingdamaged, destabilized or the like by return light.

The first non-polarizing beam splitter 13A is a known cube-shapedoptical member obtained by joining right-angle prisms (triangular prismsrespectively having isosceles right triangular bottom faces: The sameapplies to the description hereafter) with each other to be integrated,and has a joint surface 13Ah coated with, for example, a metal film. The“first non-polarizing beam splitter 13A” configures the “first lightguiding unit” according to one or more embodiments.

The non-polarizing beam splitter serves to split incident lightincluding a polarization state thereof into transmitted light andreflected light at a predetermined ratio. The same applies to thedescription hereafter. According to one or more embodiments, a so-calledhalf mirror having a split ratio of 1:1 is employed. The non-polarizingbeam splitter accordingly splits the incident light into a P-polarizedlight component and an S-polarized light component of transmitted lightand a P-polarized light component and an S-polarized light component ofreflected light all at identical rates, with keeping the respectivepolarization states of the transmitted light and the reflected lightidentical with the polarization state of the incident light.

In one or more embodiments, linearly polarized light that is polarizedin a direction parallel to the sheet surface of FIG. 1 (the Y-axisdirection or the Z-axis direction) as the polarizing direction is calledP-polarized light (P-polarized light component), and linearly polarizedlight that is polarized in the X-axis direction perpendicular to thesheet surface of FIG. 1 as the polarizing direction is calledS-polarized light (S-polarized light component).

The first non-polarizing beam splitter 13A is arranged such that one oftwo adjacent faces across the joint surface 13Ah thereof isperpendicular to the Y-axis direction and the other of the two adjacentfaces is perpendicular to the Z-axis direction. In other words, thejoint surface 13Ah of the first non-polarizing beam splitter 13A isarranged to be inclined at an angle of 45 degrees to the Y-axisdirection and the Z-axis direction. More specifically, the firstnon-polarizing beam splitter 13A is arranged such as to cause part(half) of the first light entering leftward in the Z-axis direction fromthe first light emitter 11A via the first light isolator 12A to betransmitted leftward in the Z-axis direction and such as to cause theremaining part (the remaining half) of the first light to be reflecteddownward in the Y-axis direction.

Like the first projection optical system 2A described above, the secondprojection optical system 2B includes, for example, a second lightemitter 11B, a second light isolator 12B and a second non-polarizingbeam splitter 13B. The “second light emitter 11B” configures the “secondirradiation unit” according to one or more embodiments.

Like the first light emitter 11A described above, the second lightemitter 11B includes, for example, a laser light source configured tooutput linearly polarized light having a specific wavelength λ₂, a beamexpander configured to expand the linearly polarized light output fromthe laser light source and output the expanded linearly polarized lightas parallel light, a polarizing plate configured to adjust theintensity, and a half-wave plate configured to adjust the polarizingdirection.

According to one or more embodiments under the above configuration,linearly polarized light that is polarized in a direction inclined at anangle of 45 degrees to the X-axis direction and the Z-axis direction asthe polarizing direction and that has a wavelength λ₂ (for example,λ₂=1503 nm) is emitted upward in the Y-axis direction from the secondlight emitter 11B. The “wavelength λ₂” corresponds to the “secondwavelength” according to one or more embodiments. In the descriptionbelow, the light that is emitted from the second light emitter 11B andthat has the wavelength λ₂ is called “second light”.

Like the first light isolator 12A, the second light isolator 12B is anoptical element that causes only light traveling in one direction(upward in the Y-axis direction according to one or more embodiments) tobe transmitted, while blocking light traveling in an opposite direction(downward in the Y-axis direction according to one or more embodiments).This configuration allows for transmission of only the second lightemitted from the second light emitter 11B and prevents the second lightemitter 11B from being damaged, destabilized or the like by returnlight.

Like the first non-polarizing beam splitter 13A, the secondnon-polarizing beam splitter 13B is a known cube-shaped optical memberobtained by joining right-angle prisms with each other to be integrated,and has a joint surface 13Bh coated with, for example, a metal film. The“second non-polarizing beam splitter 13B” configures the “second lightguiding unit” according to one or more embodiments.

The second non-polarizing beam splitter 13B is arranged such that one oftwo adjacent faces across the joint surface 13Bh thereof isperpendicular to the Y-axis direction and the other of the two adjacentfaces is perpendicular to the Z-axis direction. In other words, thejoint surface 13Bh of the second non-polarizing beam splitter 13B isarranged to be inclined at an angle of 45 degrees to the Y-axisdirection and the Z-axis direction. More specifically, the secondnon-polarizing beam splitter 13B is arranged such as to cause part(half) of the second light entering upward in the Y-axis direction fromthe second light emitter 11B via the second light isolator 12B to betransmitted upward in the Y-axis direction and such as to cause theremaining part (the remaining half) of the second light to be reflectedrightward in the Z-axis direction.

The following describes the configuration of the interference opticalsystem 3 in detail. The interference optical system 3 includes, forexample, a polarizing beam splitter (PBS) 20, objective lenses 21 and22, quarter-wave plates 23 and 24, a reference plane 25 and a mountingportion 26.

The polarizing beam splitter 20 is a known cube-shaped optical memberobtained by joining right-angle prisms with each other to be integrated,and has a joint surface (boundary face) 20 h coated with, for example, adielectric multi-layer film.

The polarizing beam splitter 20 serves to split linearly polarizedincident light into two polarized light components (P-polarized lightcomponent and S-polarized light component) that have polarizingdirections perpendicular to each other. The polarizing beam splitter 20according to one or more embodiments is configured to cause theP-polarized light component to be transmitted and to cause theS-polarized light component to be reflected.

The polarizing beam splitter 20 is arranged such that one of twoadjacent faces across the joint surface 20 h thereof is perpendicular tothe Y-axis direction and the other of the two adjacent faces isperpendicular to the Z-axis direction. In other words, the joint surface20 h of the polarizing beam splitter 20 is arranged to be inclined at anangle of 45 degrees to the Y-axis direction and the Z-axis direction.

More specifically, the polarizing beam splitter 20 is arranged such thata first face (Y-axis direction upper face) 20 a of the polarizing beamsplitter 20 which causes the first light reflected downward in theY-axis direction to enter from the first non-polarizing beam splitter13A described above and a third face (Y-axis direction lower face) 20 copposed to the first face 20 a are perpendicular to the Y-axisdirection. The “first face 20 a of the polarizing beam splitter 20”corresponds to the “first input-output portion” according to one or moreembodiments.

The polarizing beam splitter 20 is, on the other hand, arranged suchthat a second face (Z-axis direction left side face) 20 b of thepolarizing beam splitter 20 which causes the second light reflectedrightward in the Z-axis direction to enter from the secondnon-polarizing beam splitter 13B described above and a fourth face(Z-axis direction right side face) 20 d opposed to the second face 20 bare perpendicular to the Z-axis direction. The “second face 20 b of thepolarizing beam splitter 20” corresponds to the “second input-outputportion” according to one or more embodiments.

The objective lens 21 is arranged to be opposed in the Y-axis directionto the third face 20 c of the polarizing beam splitter 20. Thequarter-wave plate 23 is arranged to be opposed in the Y-axis directionto the objective lens 21. The reference plane 25 is arranged to beopposed in the Y-axis direction to the quarter-wave plate 23.

The objective lens 21 is arranged such that a focal position on one sideis positioned on the reference plane 25 and that focal positions on theother sides (first imaging system 4A-side and second imaging system4B-side) respectively overlap with a focal position on the other side(interference optical system 3-side) of an imaging lens 30A describedlater and with a focal position on the other side (interference opticalsystem 3-side) of an imaging lens 30B described later.

The objective lens 21 accordingly serves to cause light (referencelight) emitted from the third face 20 c of the polarizing beam splitter20 to be directed toward the reference plane 25, such as to irradiatethe reference plane 25. The objective lens 21 may be configured by alens unit consisting of a plurality of lenses or may be configured by asingle lens.

The quarter-wave plate 23 serves to convert linearly polarized lightinto circularly polarized light and to convert circularly polarizedlight into linearly polarized light. Accordingly, the linearly polarizedlight (reference light) that is emitted from the third face 20 c of thepolarizing beam splitter 20 and that passes through the objective lens21 is converted into circularly polarized light via the quarter-waveplate 23 to irradiate the reference plane 25. The reference lightreflected from the reference plane 25 is converted again from thecircularly polarized light into linearly polarized light via thequarter-wave plate 23, passes through the objective lens 21 and entersthe third face 20 c of the polarizing beam splitter 20.

The objective lens 22 is, on the other hand, arranged to be opposed inthe Z-axis direction to the fourth face 20 d of the polarizing beamsplitter 20. The quarter-wave plate 24 is arranged to be opposed in theZ-axis direction to the objective lens 22. The mounting portion 26 isarranged to be opposed in the Z-axis direction to the quarter-wave plate24.

The objective lens 22 is arranged such that a focal position on one sideis positioned on the mounting portion 26 and that focal positions on theother sides (first imaging system 4A-side and second imaging system4B-side) respectively overlap with the focal position on the other side(the interference optical system 3-side) of the imaging lens 30Adescribed later and with the focal position on the other side (theinterference optical system 3-side) of the imaging lens 30B describedlater.

The objective lens 22 accordingly serves to cause light (measurementlight) emitted from the fourth face 20 d of the polarizing beam splitter20 to be directed toward a work W that is an object to be measured or ameasurement object placed on the mounting portion 26, such as toirradiate the work W. The objective lens 22 may be configured by a lensunit consisting of a plurality of lenses or may be configured by asingle lens.

The quarter-wave plate 24 serves to convert linearly polarized lightinto circularly polarized light and to convert circularly polarizedlight into linearly polarized light. Accordingly, the linearly polarizedlight (measurement light) that is emitted from the fourth face 20 d ofthe polarizing beam splitter 20 and that passes through the objectivelens 22 is converted into circularly polarized light via thequarter-wave plate 24 to irradiate the work W that is the object to bemeasured or the measurement object placed on the mounting portion 26.The measurement light reflected from the work W is converted again fromthe circularly polarized light into linearly polarized light via thequarter-wave plate 24, passes through the objective lens 22 and entersthe fourth face 20 d of the polarizing beam splitter 20.

The following describes the configuration of the two imaging systems 4Aand 4B (the first imaging system 4A and the second imaging system 4B) indetail. The first imaging system 4A includes, for example, an imaginglens 30A, a quarter-wave plate 31A, a first polarizing plate 32A and afirst camera 33A configuring the first imaging unit.

The imaging lens 30A is arranged such that a focal position on one side(first camera 33A-side) is positioned at an imaging element 33Aadescribed later and that a focal position on the other side(interference optical system 3-side) overlaps with a focal position onthe first imaging system 4A-side of the objective lens 21 for thereference light and with a focal position on the first imaging system4A-side of the objective lens 22 for the measurement light.

The imaging lens 30A accordingly serves to cause linearly polarizedlight (a reference light component and a measurement light component ofthe first light) emitted from the second face 20 b of the polarizingbeam splitter 20 and transmitted leftward in the Z-axis directionthrough the second non-polarizing beam splitter 13B to be imaged on thefirst camera 33A (on the imaging element 33Aa). The imaging lens 30A maybe configured by a lens unit consisting of a plurality of lenses or maybe configured by one single lens.

The quarter-wave plate 31A is configured to convert each linearlypolarized light (the reference light component and the measurement lightcomponent of the first light) that is transmitted leftward in the Z-axisdirection through the second non-polarizing beam splitter 13B and thatpasses through the imaging lens 30A, into circularly polarized light.

The first polarizing plate 32A serves to cause each component of thefirst light converted into circularly polarized light by thequarter-wave plate 31A to be selectively transmitted therethrough. Thisconfiguration enables the reference light component and the measurementlight component of the first light having different rotating directionsto interfere with each other with respect to a specific phase. The“first polarizing plate 32A” configures the “phase shift unit” and the“interference unit” according to one or more embodiments.

The first polarizing plate 32A according to one or more embodiments isconfigured to be rotatable about the Z-axis direction as the axialcenter and is controlled to change a direction of a transmission axis byevery 45 degrees. More specifically, the direction of the transmissionaxis is changed to “0 degree”, “45 degrees”, “90 degrees”, and “135degrees” to the Y-axis direction.

This configuration enables the reference light component and themeasurement light component of the first light transmitted through thefirst polarizing plate 32A to interfere with each other with respect tofour different phases. This accordingly generates interference lightshaving different phases by 90 degrees each or more specificallygenerates an interference light having a phase of “0 degree”, aninterference light having a phase of “90 degrees”, an interference lighthaving a phase of “180 degrees”, and an interference light having aphase of “270 degrees”.

The first camera 33A is a known member provided with, for example, animaging element 33Aa (shown in FIG. 6 ). According to one or moreembodiments, a CCD area sensor is employed for the imaging element 33Aaof the first camera 33A. The imaging element 33Aa is, however, notlimited to this example, and, for example, a CMOS area sensor or thelike may also be employed.

Image data taken by the first camera 33A are converted into digitalsignals inside of the first camera 33A and are input in the form of thedigital signals into the control device 5 (an image data storage device54).

More specifically, an interference fringe image having the phase of “0degree”, an interference fringe image having the phase of “90 degrees”,an interference fringe image having the phase of “180 degrees” and aninterference fringe image having the phase of “270 degrees” with regardto the first light are taken by the first camera 33A.

Like the first imaging system 4A, the second imaging system 4B includes,for example, an imaging lens 30B, a quarter-wave plate 31B, a secondpolarizing plate 32B and a second camera 33B configuring the secondimaging unit.

The imaging lens 30B is arranged such that a focal position on one side(second camera 33B-side) is positioned at an imaging element 33Badescribed later and that a focal position on the other side(interference optical system 3-side) overlaps with a focal position onthe second imaging system 4B-side of the objective lens 21 for thereference light and with a focal position on the second imaging system4B-side of the objective lens 22 for the measurement light.

The imaging lens 30B accordingly serves to cause linearly polarizedlight (a reference light component and a measurement light component ofthe second light) emitted from the first face 20 a of the polarizingbeam splitter 20 and transmitted upward in the Y-axis direction throughthe first non-polarizing beam splitter 13A to be imaged on the secondcamera 33B (on the imaging element 33Ba). The imaging lens 30B may beconfigured by a lens unit consisting of a plurality of lenses or may beconfigured by one single lens.

The quarter-wave plate 31B is configured to convert each linearlypolarized light (the reference light component and the measurement lightcomponent of the second light) that is transmitted upward in the Y-axisdirection through the first non-polarizing beam splitter 13A and thatpasses through the imaging lens 30B into circularly polarized light.

Like the first polarizing plate 32A, the second polarizing plate 32Bserves to cause each component of the second light converted intocircularly polarized light by the quarter-wave plate 31B to beselectively transmitted therethrough. This configuration enables thereference light component and the measurement light component of thesecond light having different rotating directions to interfere with eachother with respect to a specific phase. The “second polarizing plate32B” configures the “phase shift unit” and the “interference unit”according to one or more embodiments.

The second polarizing plate 32B according to one or more embodiments isconfigured to be rotatable about the Y-axis direction as the axialcenter and is controlled to change a direction of a transmission axis byevery 45 degrees. More specifically, the direction of the transmissionaxis is changed to “0 degree”, “45 degrees”, “90 degrees”, and “135degrees” to the X-axis direction.

This configuration enables the reference light component and themeasurement light component of the second light transmitted through thesecond polarizing plate 32B to interfere with each other with respect tofour different phases. This accordingly generates interference lightshaving different phases by 90 degrees each or more specificallygenerates an interference light having a phase of “0 degree”, aninterference light having a phase of “90 degrees”, an interference lighthaving a phase of “180 degrees”, and an interference light having aphase of “270 degrees”.

Like the first camera 33A, the second camera 33B is a known memberprovided with, for example, an imaging element 33Ba (shown in FIG. 6 ).According to one or more embodiments, as in the case of the first camera33A, a CCD area sensor is employed for the imaging element 33Ba of thesecond camera 33B. The imaging element 33Ba is, however, not limited tothis example, and, for example, a CMOS area sensor or the like may alsobe employed.

As in the case of the first camera 33A, image data taken by the secondcamera 33B are converted into digital signals inside of the secondcamera 33B and are input in the form of the digital signals into thecontrol device 5 (the image data storage device 54).

More specifically, an interference fringe image having the phase of “0degree”, an interference fringe image having the phase of “90 degrees”,an interference fringe image having the phase of “180 degrees” and aninterference fringe image having the phase of “270 degrees” with regardto the second light are taken by the second camera 33B.

The following describes the electrical configuration of the controldevice 5. As shown in FIG. 2 , the control device 5 includes amicrocomputer 51 configured to control the entire three-dimensionalmeasurement device 1, an input device 52 serving as the “input unit”configured by a keyboard and a mouse or a touch panel, a display device53 serving as the “display unit” having a display screen such as aliquid crystal screen, an image data storage device 54 configured tosuccessively store image data and the like taken by the cameras 33A and33B, a calculation result storage device 55 configured to store theresults of various calculations, and a set data storage device 56configured to store in advance various pieces of information.

The microcomputer 51 includes, for example, a CPU 51 a serving as acomputing unit, a ROM 51 b configured to store various programs, and aRAM 51 c configured to temporarily store various data, for example,calculation data and input output data, and is electrically connectedwith the respective devices 52 to 56 described above.

The following describes the functions of the three-dimensionalmeasurement device 1. According to one or more embodiments, as describedlater, radiation of the first light and radiation of the second lightare performed simultaneously, and an optical path of the first light andan optical path of the second light partly overlap with each other. Inorder to facilitate understanding, the optical path of the first lightand the optical path of the second light are individually described withreference to different drawings.

An optical path of the first light is described first with reference toFIG. 3 . As shown in FIG. 3 , the first light having the wavelength λ₁(the linearly polarized light having the polarizing direction inclinedat 45 degrees to the X-axis direction and the Y-axis direction) isemitted leftward in the Z-axis direction from the first light emitter11A.

The first light emitted from the first light emitter 11A passes throughthe first light isolator 12A and enters the first non-polarizing beamsplitter 13A. Part of the first light entering the first non-polarizingbeam splitter 13A is transmitted leftward in the Z-direction, while theremaining part of the first light is reflected downward in the Y-axisdirection.

The first light reflected downward in the Y-axis direction (the linearlypolarized light having the polarizing direction inclined at 45 degreesto the X-axis direction and the Z-axis direction) enters the first face20 a of the polarizing beam splitter 20. The first light transmittedleftward in the Z-axis direction, on the other hand, does not enter anyoptical system but becomes unused light.

Such unused light may be utilized for measurement of the wavelength orfor measurement of the light power as needed basis. This stabilizes thelight source and enhances the accuracy of measurement.

With regard to the first light entering downward in the Y-axis directionfrom the first face 20 a of the polarizing beam splitter 20, aP-polarized light component thereof is transmitted downward in theY-axis direction and is emitted as reference light from the third face20 c, while an S-polarized light component thereof is reflectedrightward in the Z-axis direction and is emitted as measurement lightfrom the fourth face 20 d.

The reference light (the P-polarized light) with regard to the firstlight emitted from the third face 20 c of the polarizing beam splitter20 to pass through the objective lens 21 passes through the quarter-waveplate 23 to be converted into clockwise circularly polarized light andis then reflected by the reference plane 25. The rotating directionrelative to the traveling direction of light is maintained here. Thereference light with regard to the first light then passes through thequarter-wave plate 23 again to be converted from the clockwisecircularly polarized light into S-polarized light, passes through theobjective lens 21 and re-enters the third face 20 c of the polarizingbeam splitter 20.

The measurement light (the S-polarized light) with regard to the firstlight emitted from the fourth face 20 d of the polarizing beam splitter20 to pass through the objective lens 22, on the other hand, passesthrough the quarter-wave plate 24 to be converted into counterclockwisecircularly polarized light, and is then reflected by the work W. Therotating direction relative to the traveling direction of light ismaintained here. The measurement light with regard to the first lightthen passes through the quarter-wave plate 24 again to be converted fromthe counterclockwise circularly polarized light into P-polarized light,passes through the objective lens 22 and re-enters the fourth face 20 dof the polarizing beam splitter 20.

The reference light (the S-polarized light) with regard to the firstlight that re-enters the third face 20 c of the polarizing beam splitter20 is reflected leftward in the Z-axis direction by the joint surface 20h, while the measurement light (the P-polarized light) with regard tothe first light that re-enters the fourth face 20 d is transmittedleftward in the Z-axis direction through the joint surface 20 h. Acombined light obtained by combining the reference light and themeasurement light with regard to the first light with each other isemitted as output light from the second face 20 b of the polarizing beamsplitter 20.

The combined light (the reference light and the measurement light) withregard to the first light emitted from the second face 20 b of thepolarizing beam splitter 20 enters the second non-polarizing beamsplitter 13B. When the combined light with regard to the first lightenters the second non-polarizing beam splitter 13B leftward in theZ-axis direction, part of the combined light is transmitted leftward inthe Z-axis direction, and the remaining part of the combined light isreflected downward in the Y-axis direction. The combined light (thereference light and the measurement light) transmitted leftward in theZ-axis direction passes through the imaging lens 30A and enters thefirst imaging system 4A. The combined light reflected downward in theY-axis direction is, on the other hand, blocked by the second lightisolator 12B and becomes unused light.

When the combined light (the reference light and the measurement light)with regard to the first light passes through the imaging lens 30A andenters the first imaging system 4A, the quarter-wave plate 31A convertsthe reference light component (the S-polarized light component) of thecombined light into counterclockwise circularly polarized light, whileconverting the measurement light component (the P-polarized lightcomponent) into clockwise circularly polarized light. Thecounterclockwise circularly polarized light and the clockwise circularlypolarized light have different rotating directions and thus do notinterfere with each other.

The combined light with regard to the first light subsequently passesthrough the first polarizing plate 32A, so that the reference lightcomponent and the measurement light component thereof interfere witheach other in a phase corresponding to the angle of the first polarizingplate 32A. An image of such interference light with regard to the firstlight is taken by the first camera 33A.

An optical path of the second light is described next with reference toFIG. 4 . As shown in FIG. 4 , the second light having the wavelength λ₂(the linearly polarized light having the polarizing direction inclinedat 45 degrees to the X-axis direction and the Z-axis direction) isemitted upward in the Y-axis direction from the second light emitter11B.

The second light emitted from the second light emitter 11B passesthrough the second light isolator 12B and enters the secondnon-polarizing beam splitter 13B. Part of the second light entering thesecond non-polarizing beam splitter 13B is transmitted upward in theY-direction, while the remaining part of the second light is reflectedrightward in the Z-axis direction.

The second light reflected rightward in the Z-axis direction (thelinearly polarized light having the polarizing direction inclined at 45degrees to the X-axis direction and the Y-axis direction) enters thesecond face 20 b of the polarizing beam splitter 20. The second lighttransmitted upward in the Y-axis direction, on the other hand, does notenter any optical system but becomes unused light.

Such unused light may be utilized for measurement of the wavelength orfor measurement of the light power as needed basis. This stabilizes thelight source and enhances the accuracy of measurement.

With regard to the second light entering rightward in the Z-axisdirection from the second face 20 b of the polarizing beam splitter 20,an S-polarized light component thereof is reflected downward in theY-axis direction and is emitted as reference light from the third face20 c, while a P-polarized light component thereof is transmittedrightward in the Z-axis direction and is emitted as measurement lightfrom the fourth face 20 d.

The reference light (the S-polarized light) with regard to the secondlight emitted from the third face 20 c of the polarizing beam splitter20 to pass through the objective lens 21 passes through the quarter-waveplate 23 to be converted into counterclockwise circularly polarizedlight and is then reflected by the reference plane 25. The rotatingdirection relative to the traveling direction of light is maintainedhere. The reference light with regard to the second light then passesthrough the quarter-wave plate 23 again to be converted from thecounterclockwise circularly polarized light into P-polarized light,passes through the objective lens 21 and re-enters the third face 20 cof the polarizing beam splitter 20.

The measurement light (the P-polarized light) with regard to the secondlight emitted from the fourth face 20 d of the polarizing beam splitter20 to pass through the objective lens 22, on the other hand, passesthrough the quarter-wave plate 24 to be converted into clockwisecircularly polarized light, and is then reflected by the work W. Therotating direction relative to the traveling direction of light ismaintained here. The measurement light with regard to the second lightthen passes through the quarter-wave plate 24 again to be converted fromthe clockwise circularly polarized light into S-polarized light, passesthrough the objective lens 22 and re-enters the fourth face 20 d of thepolarizing beam splitter 20.

The reference light (the P-polarized light) with regard to the secondlight that re-enters the third face 20 c of the polarizing beam splitter20 is transmitted upward in the Y-axis direction through the jointsurface 20 h, while the measurement light (the S-polarized light) withregard to the second light that re-enters the fourth face 20 d isreflected upward in the Y-axis direction by the joint surface 20 h. Acombined light obtained by combining the reference light and themeasurement light with regard to the second light with each other isemitted as output light from the first face 20 a of the polarizing beamsplitter 20.

The combined light (the reference light and the measurement light) withregard to the second light emitted from the first face 20 a of thepolarizing beam splitter 20 enters the first non-polarizing beamsplitter 13A. When the combined light with regard to the second lightenters the first non-polarizing beam splitter 13A upward in the Y-axisdirection, part of the combined light is transmitted upward in theY-axis direction, and the remaining part of the combined light isreflected rightward in the Z-axis direction. The combined light (thereference light and the measurement light) transmitted upward in theY-axis direction passes through the imaging lens 30B and enters thesecond imaging system 4B. The combined light reflected rightward in theZ-axis direction is, on the other hand, blocked by the first lightisolator 12A and becomes unused light.

When the combined light (the reference light and the measurement light)with regard to the second light passes through the imaging lens 30B andenters the second imaging system 4B, the quarter-wave plate 31B convertsthe reference light component (the P-polarized light component) of thecombined light into clockwise circularly polarized light, whileconverting the measurement light component (the S-polarized lightcomponent) into counterclockwise circularly polarized light. Thecounterclockwise circularly polarized light and the clockwise circularlypolarized light have different rotating directions and thus do notinterfere with each other.

The combined light with regard to the second light subsequently passesthrough the second polarizing plate 32B, so that the reference lightcomponent and the measurement light component thereof interfere witheach other in a phase corresponding to the angle of the secondpolarizing plate 32B. An image of such interference light with regard tothe second light is taken by the second camera 33B.

The following describes a procedure of a measurement process performedby the control device 5 in detail with reference to the flowchart ofFIG. 5 and other drawings. In the following description of thismeasurement process, it is assumed that an x-y plane is assumed to beeither an imaging element 33Aa-face of the first camera 33A or animaging element 33Ba-face of the second camera 33B and that a zdirection is a direction of an optical axis perpendicular thereto. Thiscoordinate system (x, y, z) is a different coordinate system from acoordinate system (X, Y, Z) used to described the entirethree-dimensional measurement device 1.

At step S1, the control device 5 first performs a process of obtaininginterference fringe images with regard to a predetermined measurementarea of the work W (the entirety or part of the work W). According toone or more embodiments, the control device 5 obtains four differentinterference fringe images having different phases with regard to thefirst light and four different interference fringe images havingdifferent phases with regard to the second light. This is described morein detail below.

After placement of the work W on the mounting portion 26, the controldevice 5 sets the direction of the transmission axis of the firstpolarizing plate 32A in the first imaging system 4A to a predeterminedreference position (for example, “0 degree”) and sets the direction ofthe transmission axis of the second polarizing plate 32B in the secondimaging system 4B to a predetermined reference position (for example, “0degree”).

The control device 5 subsequently causes the first light to be radiatedfrom the first projection optical system 2A and simultaneously causesthe second light to be radiated from the second projection opticalsystem 2B. As a result, the combined light (the reference light and themeasurement light) with regard to the first light is emitted from thesecond face 20 b of the polarizing beam splitter 20 in the interferenceoptical system 3, and at the same time, the combined light (thereference light and the measurement light) with regard to the secondlight is emitted from the first face 20 a of the polarizing beamsplitter 20.

An image of the combined light with regard to the first light emittedfrom the second face 20 b of the polarizing beam splitter 20 is taken bythe first imaging system 4A, while an image of the combined light withregard to the second light emitted from the first face 20 a of thepolarizing beam splitter 20 is taken by the second imaging system 4B.

In this state, the direction of the transmission axis of the firstpolarizing plate 32A and the direction of the transmission axis of thesecond polarizing plate 32B are respectively set to “0 degree”, so thatthe first camera 33A takes an interference fringe image having the phaseof “0 degree” with regard to the first light, and the second camera 33Btakes an interference fringe image having the phase of “0 degree” withregard to the second light.

Image data respectively taken are output from the respective cameras 33Aand 33B to the control device 5. The control device 5 stores the inputimage data into the image data storage device 54.

The control device 5 subsequently performs a switching process ofswitching between the first polarizing plate 32A of the first imagingsystem 4A and the second polarizing plate 32B of the second imagingsystem 4B. More specifically, the control device 5 respectively rotatesand shifts the first polarizing plate 32A and the second polarizingplate 32B to respective positions having the directions of transmissionaxis equal to “45 degrees”.

On completion of the switching process, the control device 5 performs asecond imaging process similar to the series of the first imagingprocess described above. More specifically, the control device 5 causesthe first light to be radiated from the first projection optical system2A and simultaneously causes the second light to be radiated from thesecond projection optical system 2B. The control device 5 then causes animage of the combined light with regard to the first light emitted fromthe second face 20 b of the polarizing beam splitter 20 to be taken bythe first imaging system 4A and at the same time causes an image of thecombined light with regard to the second light emitted from the firstface 20 a of the polarizing beam splitter 20 to be taken by the secondimaging system 4B. The control device 5 accordingly obtains aninterference fringe image having the phase of “90 degrees” with regardto the first light and obtains an interference fringe image having thephase of “90 degrees” with regard to the second light.

Two more imaging processes similar to the first imaging process and thesecond imaging process described above are repeated. More specifically,the control device 5 performs a third imaging process in the state thatthe respective directions of transmission axis of the first polarizingplate 32A and the second polarizing plate 32B are set to “90 degrees” toobtain an interference fringe image having the phase of “180 degrees”with regard to the first light and obtain an interference fringe imagehaving the phase of “180 degrees” with regard to the second light.

The control device 5 subsequently performs a fourth imaging process inthe state that the respective directions of transmission axis of thefirst polarizing plate 32A and the second polarizing plate 32B are setto “135 degrees” to obtain an interference fringe image having the phaseof “270 degrees” with regard to the first light and obtain aninterference fringe image having the phase of “270 degrees” with regardto the second light.

Performing the four imaging processes as described above obtains all theimage data required for measurement relating to the predeterminedmeasurement area of the work W (a total of eight interference fringeimages consisting of four interference fringe images with regard to thefirst light and four interference fringe images with regard to thesecond light).

At subsequent step S2, the control device 5 performs a process ofobtaining complex amplitude data of light on the imaging element33Aa-face or on the imaging element 33Ba-face.

According to one or more embodiments, the control device 5 obtainscomplex amplitude data Eo(x,y) of light on the imaging element 33Aa-faceor on the imaging element 33Ba-face with regard to each of the firstlight and the second light, based on the four interference fringe imageswith regard to the first light and the four interference fringe imageswith regard to the second light stored in the image data storage device54.

Interference fringe intensities, i.e., luminances I₁(x,y), I₂(x,y),I₃(x,y) and I₄(x,y), at an identical coordinate position (x,y) in thefour interference fringe images with regard to the first light or withregard to the second light are expressed by relational expressions of[Math. 1] given below:

I ₁(x,y)=B(x,y)+A(x,y)cos[Δϕ(x,y)]

I ₂(x,y)=B(x,y)+A(x,y)cos[Δϕ(x,y)+90°]

I ₃(x,y)=B(x,y)+A(x,y)cos[Δϕ(x,y)+180°]

I ₄(x,y)=B(x,y)+A(x,y)cos[Δϕ(x,y)+270°]  [Math. 1]

Herein Δϕ(x,y) denotes a phase difference based on an optical pathdifference between the measurement light and the reference light at thecoordinates (x,y); A(x,y) denotes an amplitude of interference light;and B(x,y) denotes a bias. Since the reference light is uniform, fromthis viewpoint as the basis, Δϕ(x,y) denotes a “phase of the measurementlight” and A(x,y) denotes an “amplitude of the measurement light”.

Accordingly, the phase Δϕ(x,y) of the measurement light reaching theimaging element 33Aa-face or the imaging element 33Ba-face is determinedfrom a relational expression of [Math. 2] given below, based on therelational expressions of [Math. 1] given above:

$\begin{matrix}{{\Delta{\phi\left( {x,y} \right)}} = {\arctan\frac{{I_{4}\left( {x,y} \right)} - {I_{2}\left( {x,y} \right)}}{{I_{1}\left( {x,y} \right)} - {I_{3}\left( {x,y} \right)}}}} & \left\lbrack {{Math}.2} \right\rbrack\end{matrix}$

An amplitude A(x,y) of the measurement light reaching the imagingelement 33Aa-face or the imaging element 33Ba-face is determined from arelational expression of [Math. 3] given below, based on the relationalexpressions of [Math. 1] given above:

$\begin{matrix}{{A\left( {x,y} \right)} = {\frac{1}{2} \times \sqrt{\left\{ {{I_{1}\left( {x,y} \right)} - {I_{3}\left( {x,y} \right)}} \right\}^{2} + \left\{ {{I_{4}\left( {x,y} \right)} - {I_{2}\left( {x,y} \right)}} \right\}^{2}}}} & \left. \left\{ {{Math}.3} \right. \right\rbrack\end{matrix}$

The complex amplitude data Eo(x,y) on the imaging element 33Aa-face oron the imaging element 33Ba-face is calculated from the phase Δϕ(x,y)and the amplitude A(x,y) described above according to a relationalexpression of [Math. 4] given below, where I denotes an imaginary unit:

E ₀(x,y)=A(x,y)e ^(iϕ(x,y))  [Math. 4]

At subsequent step S3, the control device 5 performs a process ofobtaining complex amplitude data at a plurality of positions in the zdirection with regard to a specific area V (shown in FIG. 7 ) that is apart set in advance in the measurement area on the work W.

According to one or more embodiments, the control device 5 obtainscomplex amplitude data with regard to the specific area V at everypredetermined measurement range interval in a predetermined range Q1 inthe z direction (in a first range in the direction of the optical axis)where the work W is likely to be present, on the basis of a deviceorigin that is a standard of height measurement in the three-dimensionalmeasurement device 1.

The “specific area V” herein is an area arbitrarily set to grasp theposition of the work W in the z direction in advance. For example, whenthe work W is a wafer substrate 100 as shown in FIGS. 8 and 9 , apattern portion 102 that is served as a reference plane for heightmeasurement of a bump 101 is set as the specific area V.

A measurement example of the wafer substrate 100 shown in FIG. 8 isconfigured to obtain complex amplitude data at height positions H₃, H₂,H₁, H₀, H⁻¹, H⁻² and H⁻³ set at every measurement range interval R inthe vertical direction from a device origin H₀, as the center, that isthe standard of height measurement in the three-dimensional measurementdevice 1.

The following describes the method of obtaining the complex amplitudedata at step S3 in detail. The description first refers to a method ofobtaining unknown complex amplitude data at a different position in thez direction from known complex amplitude data at a predeterminedposition in the z direction.

Two coordinate systems (an x-y coordinate system and a ξ-η coordinatesystem) that are away from each other by a distance d in the z directionare assumed here. A relationship shown by [Math. 5] given below isobtained by expressing the x-y coordinate system as z=0, known complexamplitude data of light in the x-y coordinate system as Eo(x,y) andunknown complex amplitude data of light in a ξ-η plane away from the x-yplane by the distance d as Eo(ξ,η), where λ denotes a wavelength.

$\begin{matrix}\begin{matrix}{{E_{0}\left( {x,y} \right)} = {\frac{i}{\lambda}{\int\limits_{- \infty}^{\infty}{\int\limits_{- \infty}^{\infty}{{E_{0}\left( {\xi,\eta} \right)}\frac{\exp\left( {{- i}\frac{2\pi}{\lambda}\sqrt{\begin{matrix}{d^{2} + \left( {\xi - x} \right)^{2} +} \\\left( {\eta - y} \right)^{2}\end{matrix}}} \right)}{\sqrt{d^{2} + \left( {\xi - x} \right)^{2} + \left( {\eta - y} \right)^{2}}}d\xi d\eta}}}}} \\{= {\mathcal{F}^{- 1}\left\{ {{\mathcal{F}\left( {E_{0}\left( {\xi,\eta} \right)} \right)} \cdot {\mathcal{F}\left( {g\left( {\xi,\eta,x,y} \right)} \right)}} \right\}}}\end{matrix} & \left\lbrack {{Math}.5} \right\rbrack\end{matrix}$${g\left( {\xi,\eta,x,y} \right)} = {\frac{i}{\lambda}\frac{\exp\left( {{- i}\frac{2\pi}{\lambda}\sqrt{d^{2} + \left( {\xi - x} \right)^{2} + \left( {\eta - y} \right)^{2}}} \right)}{\sqrt{d^{2} + \left( {\xi - x} \right)^{2} + \left( {\eta - y} \right)^{2}}}}$ℱ : Fouriertransform ℱ⁻¹ : inverseFouriertransform

An expression of [Math. 6] given below is obtained by solving thisrelational expression with regard to Eo(ξ,η)

$\begin{matrix}{{E_{0}\left( {\xi,\eta} \right)} = {\mathcal{F}^{- 1}\left\{ \frac{\mathcal{F}\left( {E_{0}\left( {x,y} \right)} \right)}{\mathcal{F}\left( {g\left( {\xi,\eta,x,y} \right)} \right)} \right\}}} & \left\lbrack {{Math}.6} \right\rbrack\end{matrix}$

Accordingly, at step S3, complex amplitude data EoL0(ξ,η), EoL1(ξ,η), .. . , EoLn(ξ,η) at positions away from the imaging element 33Aa-face orthe imaging element 33Ba-face by a distance L=L0, L1, L2, . . . , Ln inthe z direction (z=L0, L1, . . . , Ln) are obtained, based on thecomplex amplitude data Eo(x,y) on the imaging element 33Aa-face or onthe imaging element 33Ba-face obtained at step S2 described above, asshown in FIGS. 6 and 7 .

At subsequent step S4, the control device 5 performs process ofobtaining intensity image (luminance image) data at a plurality ofpositions in the z direction with regard to the specific area V.

More specifically, the control device 5 obtains intensity image datafrom the respective complex amplitude data EoL0(ξ,η), EoL1(ξ,η), . . . ,EoLn(ξ,η) at the plurality of positions in the z direction with regardto the specific area V obtained at step S3 described above. Accordingly,the function of performing the series of reconstruction process at stepsS2 to S4 described above configures the first image data obtaining unitaccording to one or more embodiments.

When the complex amplitude data in the ξ-η plane is expressed asEo(ξ,η), intensity image data I(ξ,η) in the ξ-η plane is determinedaccording to a relational expression of [Math. 7] given below]

I(ξ,η)=|E ₀(ξ,η)|²  [Math. 7]

At subsequent step S5, the control device 5 performs a process ofdetermining an optimum focusing position (focusing position in thedirection of the optical axis) with regard to the specific area V. Thefunction of performing this process of step S5 configures the firstfocusing position determination unit according to one or moreembodiments.

More specifically, the control device 5 determines an optimum focusingposition in the z direction with regard to the specific area V, based onthe intensity image data at the plurality of positions in the zdirection with regard to the specific area V obtained at step S4described above. The following describes a method of determining theoptimum focusing position with regard to the specific area V from thecontrast of the intensity image data.

This method first determines a contrast between a luminance at a“specific coordinate position” and a luminance at “another coordinateposition”, based on the intensity image data of the specific area V atthe respective positions in the z direction (z=L0, L1, . . . , Ln) awayfrom the imaging element 33Aa-face or the imaging element 33Ba-face inthe z direction by the distance L=L0, L1, L2, . . . , Ln. The methodsubsequently extracts a position (z=Lm) where the intensity image dataof the highest contrast is obtained, as the optimum focusing position.

The method of determining the optimum focusing position with regard tothe specific area V is not limited to this method of determination fromthe contrast of the intensity image data described above, but anothermethod, for example, a method of determination from the luminance of theintensity image data, may be employed.

This latter method takes advantage of the characteristic of theintensity image data that has the highest luminance on a face where anobject is actually present. More specifically, this method determines anaverage luminance at each of coordinate position in the specific area V,based on the intensity image data with regard to the specific area V atthe respective positions in the z direction (z=L0, L1, . . . , Ln). Themethod subsequently extracts a position (z=Lm) where the intensity imagedata of the highest average luminance is obtained, as the optimumfocusing position.

For example, in the measurement example of the wafer substrate 100 shownin FIG. 8 , the control device 5 determines the contrast or the averageluminance with regard to the intensity image data of the pattern portion102 at the height positions H₃, H₂, H₁, H₀, H⁻¹, H⁻² and H⁻³ andextracts the position where the intensity image data of the highestcontrast or the intensity image data of the highest average luminance(for example, the height position H⁻¹) among these intensity image data,as the optimum focusing position.

At subsequent step S6, the control device 5 performs a process ofobtaining complex amplitude data at a plurality of positions in the zdirection with regard to each of coordinate positions in the entirety ofthe predetermined measurement area of the work W.

According to one or more embodiments, the control device 5 obtainscomplex amplitude data with regard to each of the coordinate positionsin the measurement area at every predetermined measurement rangeinterval in a predetermined range Q2 in the z direction (in a secondrange in the direction of the optical axis) where a predeterminedmeasurement target on the work W (for example, a bump 101 on the wafersubstrate 100) is likely to be present, on the basis of the optimumfocusing position with regard to the specific area V determined at stepS5 described above.

For example, the measurement example of the wafer substrate 100 shown inFIG. 8 is configured to obtain complex amplitude data at the respectiveheight positions H₁, H₀ and H⁻¹ set at every measurement range intervalR in an upward direction, on the basis of the optimum focusing position(height position H⁻¹) of the specific area V.

In the example shown in FIG. 8 , the predetermined range Q2 in the zdirection is set to be narrower than the predetermined range Q1 in the zdirection. This is, however, not essential. The predetermined range Q2in the z direction may be set to be identical with or may be set to bewider than the predetermined range Q1 in the z direction. In thisregard, however, the predetermined range Q2 in the z direction may beset to be narrower than the predetermined range Q1 in the z direction,in terms of reducing the load of the process of obtaining data requiredfor three-dimensional measurement with regard to each of the coordinatepositions in the entire measurement area and shortening the time periodrequired for this process.

The method of obtaining the complex amplitude data at step S6 is similarto the method of obtaining the complex amplitude data at step S3described above and is thus not described in detail.

At subsequent step S7, the control device 5 performs a process ofobtaining intensity image data at a plurality of positions in the zdirection, with regard to each of the coordinate positions in themeasurement area on the work W. Accordingly, the function of performingthe series of processes at steps S6 and S7 described above configuresthe second image data obtaining unit according to one or moreembodiments.

More specifically, the control device 5 obtains intensity image data ata plurality of positions in the z direction, with regard to each of thecoordinate positions in the measurement area on the work W, based on thecomplex amplitude data obtained at step S6 described above. The methodof obtaining the intensity image data from the complex amplitude data atstep S7 is similar to the method of obtaining the intensity image dataat step S4 described above and is thus not described in detail.

At subsequent step S8, the control device 5 performs a process ofdetermining an optimum focusing position (focusing position in thedirection of the optical axis) with regard to each of the coordinatepositions in the measurement area on the work W. The function ofperforming this process of step S8 configures the second focusingposition determination unit according to one or more embodiments.

More specifically, the control device 5 determines the optimum focusingposition in the z direction with regard to each of the coordinatepositions in the measurement area, based on the intensity image data atthe plurality of positions in the z direction with regard to each of thecoordinate positions in the measurement area obtained at step S7described above. The method of determining the optimum focusing positionfrom the intensity image data at the plurality of positions in the zdirection at step S8 is similar to the method of determining the optimumfocusing position at step S5 described above and is thus not describedin detail.

At subsequent step S9, the control device 5 performs a process ofspecifying an order corresponding to the optimum focusing position withregard to each of the coordinate positions in the measurement area onthe work W determined at step S8, as an order of a measurement rangewith regard to each of the coordinate positions. The function ofperforming this process of step S9 configures the order specificationunit according to one or more embodiments.

A method of specifying the order of the measurement range is describedbelow with reference to a concrete example illustrated in FIG. 11 . Inthe example illustrated in FIG. 11 , the wafer substrate 100 shown inFIG. 8 is subjected to height measurement in a range of “−3500 (nm)” to“3500 (nm)” by using light having a measurement range (corresponding toone period [−180 degrees to 180 degrees] of a sinusoidal wave in a phaseshift method) of 1000 nm (composite wavelength light of two wavelengthsaccording to one or more embodiments).

In a “Case 1” shown in FIG. 11 , among intensity image datareconstructed at height positions H₃, H₂, H₁, H₀, H⁻¹, H⁻² and H⁻³(reconstructed images [1] to [7]) with regard to a predeterminedcoordinate position, the intensity image data reconstructed at theheight position H₂ (reconstructed image [2]) has a maximum luminancevalue of “250”. Accordingly, the height position H₂ is specified as theoptimum focusing position with regard to this coordinate position, andthe order [2] corresponding to this optimum focusing position isspecified as the order of the measurement range with regard to thiscoordinate position.

In “Case 2” shown in FIG. 11 , among intensity image data reconstructedat height positions H₃, H₂, H₁, H₀, H⁻¹, H⁻² and H⁻³ (reconstructedimages [1] to [7]) with regard to a predetermined coordinate position,both the intensity image data reconstructed at the height position H₂(reconstructed image [2]) and the intensity image data reconstructed atthe height position H₁ (reconstructed image [1]) have a maximumluminance value of “128”.

In this case, the actual height with regard to this coordinate positionis expected to be a height corresponding to the vicinity of the boundarybetween the measurement range of the order [2] and the measurement rangeof the order [1]. At this time, the two orders [2] and [1] are specifiedas the orders of the measurement range with regard to this coordinateposition.

At subsequent step S10, the control device 5 performs athree-dimensional measurement process. The function of performing thisprocess of step S10 configures the three-dimensional measurement unitaccording to one or more embodiments.

The control device 5 first calculates a phase ϕ(ξ,η) of the measurementlight and an amplitude A(ξ,η) of the measurement light from the complexamplitude data Eo(ξ,η) at the optimum focusing position with regard toeach of the coordinate positions in the measurement area determined atstep S8, according to a relational expression of [Math. 8] given below:

E ₀(ξ,η)=A(ξ,η)e ^(iϕ(ξ,η))  [Math. 8]

The phase ϕ(ξ,η) of the measurement light is determined according to arelational expression of [Math. 9] given below. The function ofperforming the series of reconstruction process to calculate the phaseϕ(ξ,η) that is the phase information of the measurement light configuresthe phase information obtaining unit according to one or moreembodiments.

$\begin{matrix}{{\phi\left( {\xi,\eta} \right)} = {\arctan\frac{{Im}\left\lbrack {E_{0}\left( {\xi,\eta} \right)} \right\rbrack}{{Re}\left\lbrack {E_{0}\left( {\xi,\eta} \right)} \right\rbrack}}} & \left\lbrack {{Math}.9} \right\rbrack\end{matrix}$

The amplitude A(ξ,η) of the measurement light is determined according toa relational expression of [Math. 10] given below:

A(ξ,η)=√{square root over ((Re[E ₀(ξ,η)])²+(Im[E ₀(ξ,η)])²)}  [Math. 10]

The control device 5 subsequently performs a phase-height conversionprocess and calculates height information z(ξ,η) in the measurementrange that shows the surface roughness or the concavo-convexconfiguration on the surface of the work W in a three-dimensionalmanner.

The height information z(ξ,η) in the measurement range is calculatedaccording to a relational expression of [Math. 11] given below:

$\begin{matrix}{{Z\left( {\xi,\eta} \right)} = {\frac{1}{2}{\phi\left( {\xi,\eta} \right)}\frac{\lambda}{2\pi}}} & \left\lbrack {{Math}.11} \right\rbrack\end{matrix}$

The control device 5 then obtains true height data (actual height) withregard to each coordinate position, based on the height informationz(ξ,η) in the measurement range calculated as described above and theorder of the measurement range with regard to the coordinate positionspecified at step S9.

For example, in the example illustrated in FIG. 11 , in the case wherethe height information z(ξ,η) in the measurement range calculated asdescribed above with regard to a predetermined coordinate positioncorresponds to a phase “+90 degrees”, candidates of true height datawith regard to the coordinate position are “3250 (nm)” of the order [3],“2250 (nm)” of the order [2], “1250 (nm)” of the order [1], “250 (nm)”of the order [0], “−750 (nm)” of the order [−1], “−1750 (nm)” of theorder [−2], and “−2750 (nm)” of the order [−3].

As in the “Case 1”, for example, when the height position H₂ is theoptimum focusing position with regard to the coordinate position and thecorresponding order [2] is specified as the order of the measurementrange with regard to the coordinate position, the true height data withregard to the coordinate position is specified as “2250 (nm)”corresponding to the phase “90 degrees” of the order [2].

In another example, in the example illustrated in FIG. 11 , in the casewhere the height information z(ξ,η) in the measurement range calculatedas described above with regard to a predetermined coordinate positioncorresponds to a phase “−180 degrees”, candidates of true height datawith regard to the coordinate position are “2500 (nm)” of the order [3],“1500 (nm)” of the order [2], “500 (nm)” of the order [1], “−500 (nm)”of the order [0], “−1500 (nm)” of the order [−1], “−2500 (nm)” of theorder [−2], and “3500 (nm)” of the order [−3].

As in the “Case 2”, for example, when the height position H₂ and theheight position H₁ are the optimum focusing positions with regard to thecoordinate position and the corresponding order [2] and thecorresponding order [1] are specified as the orders of the measurementrange with regard to the coordinate position, the true height data withregard to the coordinate position is specified as “1500 (nm)”corresponding to the phase “−180 degrees” of the order [2].

In the case where the work W is a wafer substrate 100 (shown in FIG. 9 )and a bump 101 is a measurement target, a height HB of the bump 101relative to a pattern portion 102 as a measurement reference plane isdetermined by subtracting an absolute height HA2 of the pattern portion102 in the periphery of the bump 101 from an absolute height HA1 of thebump 101 [HB=HA1−HA2].

The absolute height HA2 of the pattern portion 102 may be, for example,an absolute height at one arbitrary point on the pattern portion 102 oran average value of absolute heights in a predetermined range on thepattern portion 102. The “absolute height HA1 of the bump 101” and the“absolute height HA2 of the pattern portion 102” may be determined fromthe height information z(ξ,η) and the order of the measurement range.

The results of the measurement of the work W determined as describedabove are stored in the calculation result storage device 55 of thecontrol device 5.

The measurement using two different types of lights having differentwavelengths (wavelengths λ₁ and λ₂) is equivalent to the measurementusing the light of the composite wavelength λ₀. The measurement rangethereof is expanded to λ₀/2. The composite wavelength λ₀ is expressed byExpression (M1) given below:

λ₀=(λ₁×λ₂)/(λ₂−λ₁)  (M1)

where λ₂>λ₁.

For example, when λ₁=1500 nm and λ₂=1503 nm, λ₀=751.500 μm according toExpression (M1) given above, and the measurement range λ₀/2=375.750 μm.

This is described more in detail. According to one or more embodiments,a phase ϕ₁(ξ,η) of measurement light with regard to a first light havinga wavelength λ₁ at coordinates (ξ,η) on a work W-surface is calculated(refer to [Math. 9] given above), based on luminances I₁(x,y), I₂(x,y),I₃(x,y) and I₄(x,y) of four different interference fringe images withregard to the first light (refer to [Math. 1] given above).

Under the measurement with regard to the first light, height informationz(ξ,η) at the coordinates (ξ,η) is expressed by Expression (M2) givenbelow:

$\begin{matrix}\begin{matrix}{{z\left( {\xi,\eta} \right)} = {{d_{1}\left( {\xi,\eta} \right)}/2}} \\{= {\left\{ {\lambda_{1} \times {{\phi_{1}\left( {\xi,\eta} \right)}/4}\pi} \right\} + \left\{ {{m_{1}\left( {\xi,\eta} \right)} \times {\lambda_{1}/2}} \right\}}}\end{matrix} & \left( {M2} \right)\end{matrix}$

where d₁(ξ,η) denotes an optical path difference between measurementlight and reference light with regard to the first light, and m₁(ξ,η)denotes a fringe order with regard to the first light.

Accordingly, the phase ϕ₁(ξ,η) is expressed by Expression (M2′) givenbelow:

ϕ₁(ξ,η)=(4π/λ₁)×z(ξ,η)−2πm ₁(ξ,η)  (M2′)

Similarly, a phase ϕ₂(ξ,η) of measurement light with regard to a secondlight having a wavelength λ₂ at coordinates (ξ,η) on the work W-surfaceis calculated (refer to [Math. 9] given above), based on luminancesI₁(x,y), I₂(x,y), I₃(x,y) and I₄(x,y) of four different interferencefringe images with regard to the second light (refer to [Math. 1] givenabove).

Under the measurement with regard to the second light, heightinformation z(ξ,η) at the coordinates (ξ,η) is expressed by Expression(M3) given below:

$\begin{matrix}\begin{matrix}{{z\left( {\xi,\eta} \right)} = {{d_{2}\left( {\xi,\eta} \right)}/2}} \\{= {\left\{ {\lambda_{2} \times {{\phi_{2}\left( {\xi,\eta} \right)}/4}\pi} \right\} + \left\{ {{m_{2}\left( {\xi,\eta} \right)} \times {\lambda_{2}/2}} \right\}}}\end{matrix} & \left( {M3} \right)\end{matrix}$

where d₂(ξ,η) denotes an optical path difference between measurementlight and reference light with regard to the second light, and m₂(ξ,η)denotes a fringe order with regard to the second light.

Accordingly, the phase ϕ₂(ξ,η) is expressed by Expression (M3′) givenbelow:

ϕ₂(ξ,η)=(4π/λ₂)×z(ξ,η)−2πm ₂(ξ,η)  (M3′)

The fringe order m₁(ξ,η) with regard to the first light having thewavelength λ₁ and the fringe order m₂(ξ,η) with regard to the secondlight having the wavelength λ₂ are determined, based on an optical pathdifference Δd and a wavelength difference Δλ between the two differenttypes of lights (the wavelengths λ₁ and λ₂). The optical path differenceΔd and the wavelength difference Δλ are respectively expressed byExpressions (M4) and (M5) given below:

Δd=(λ₁×ϕ₁−λ₂×ϕ₂)/2π  (M4)

Δλ=λ₁−λ₁  (M5)

where λ₂>λ₁.

In the measurement range of the composition wavelength λ₀ of the twowavelengths, the relationship between the fringe orders m₁ and m₂ isclassified into the following three cases: each case employs a differentcomputational expression to determine the fringe orders m₁(ξ,η) andm₂(ξ,η). The following describes a procedure of determining, forexample, the fringe order m₁(ξ,η). A similar procedure is employed todetermine the fringe order m₂(ξ,η).

For example, in the case of “ϕ₁−ϕ₂<−π”, “m₁−m₂=−1”. In this case, m₁ isexpressed by Expression (M6) given below:

$\begin{matrix}\begin{matrix}{m_{1} = {\left( {\Delta{d/\Delta}\lambda} \right) \cdot \left( {{\lambda_{2}/\Delta}\lambda} \right)}} \\{= {{{\left( {{\lambda_{1} \times \phi_{1}} - {\lambda_{2} \times \phi_{2}}} \right)/2}{\pi\left( {\lambda_{2} - \lambda_{1}} \right)}} - {\lambda_{2}/\left( {\lambda_{2} - \lambda_{1}} \right)}}}\end{matrix} & ({M6})\end{matrix}$

In the case of “π<ϕ₁−ϕ₂<π”, “m₁−m₂=0”. In this case, m₁ is expressed byExpression (M7) given below:

$\begin{matrix}\begin{matrix}{m_{1} = {\Delta{d/\Delta}\lambda}} \\{= {{\left( {{\lambda_{1} \times \phi_{1}} - {\lambda_{2} \times \phi_{2}}} \right)/2}{\pi\left( {\lambda_{2} - \lambda_{1}} \right)}}}\end{matrix} & ({M7})\end{matrix}$

In the case of “ϕ₁−ϕ₂>π”, “m₁−m₂=+1”. In this case, m₁ is expressed byExpression (M8) given below:

$\begin{matrix}\begin{matrix}{m_{1} = {\left( {\Delta{d/\Delta}\lambda} \right) + \left( {{\lambda_{2}/\Delta}\lambda} \right)}} \\{= {{{\left( {{\lambda_{1} \times \phi_{1}} - {\lambda_{2} \times \phi_{2}}} \right)/2}{\pi\left( {\lambda_{2} - \lambda_{1}} \right)}} + {\lambda_{2}/\left( {\lambda_{2} - \lambda_{1}} \right)}}}\end{matrix} & ({M8})\end{matrix}$

The height information z(ξ,η) is obtained according to Expression (M2)or Expression (M3) given above, based on the fringe order m₁(ξ,η) or thefringe order m₂(ξ,η) obtained as described above.

As described above in detail, the configuration of one or moreembodiments allows for height measurement exceeding the measurementrange with regard to each of the coordinate positions in the measurementarea on the work W. This configuration is simplified without requiringany large-scaled moving mechanism such as to move the work and is notaffected by the vibration or the like of the moving mechanism, andaccordingly achieves the improvement of the measurement accuracy.

Furthermore, the configuration of one or more embodiments enables allthe interference fringe images required for the measurement to beobtained by the less number of times of imaging and thereby enhances themeasurement efficiency.

Additionally, the configuration of one or more embodiments first obtainsthe intensity image data at a plurality of positions in the z directionwith regard to not the entire measurement area on the work W but withregard to only a specific area V that is part of the measurement areaset in advance, specifies the position of the work W in the z directionbased on the focusing state of the obtained intensity image data,subsequently obtains the intensity image data at a plurality ofpositions in the z direction with regard to each of the coordinatepositions in the entire measurement area, on the basis of the specifiedposition, and then performs measurement.

This configuration reduces the load of the process of obtaining datarequired for three-dimensional measurement with regard to themeasurement area and shortens the time period required for this process.As a result, the configuration of one or more embodiments improves themeasurement accuracy and enhances the measurement efficiency.

Moreover, the configuration of one or more embodiments causes the firstlight having the wavelength λ1 to enter the first face 20 a of thepolarizing beam splitter 20 and causes the second light having thewavelength λ2 to enter the second face 20 b of the polarizing beamsplitter 20 and thereby enables the reference light and the measurementlight with regard to the first light and the reference light and themeasurement light with regard to the second light to be split intodifferent polarized light components (P-polarized light or S-polarizedlight). The first light and the second light entering the polarizingbeam splitter 20 accordingly do not interfere with each other but areseparately emitted from the polarizing beam splitter 20. Theconfiguration of one or more embodiments accordingly does not require touse a predetermined separation unit to separate the light emitted fromthe polarizing beam splitter 20 into first light and second light.

As a result, the configuration of one or more embodiments enables thetwo different types of lights having the wavelengths close to each otherto be used as the first light and the second light and further expandsthe measurement range in three-dimensional measurement. Additionally,the configuration of one or more embodiments enables imaging of theoutput light with regard to the first light and imaging of the outputlight with regard to the second light to be performed simultaneously.This shortens the total imaging time and enhances the measurementefficiency.

Additionally, the configuration of one or more embodiments is providedwith the objective lens 21 that causes light (reference light) emittedfrom the third face 20 c of the polarizing beam splitter 20 to bedirected toward the reference plane 25 such as to irradiate thereference plane 25 and with the objective lens 22 that causes light(measurement light) emitted from the fourth face 20 d of the polarizingbeam splitter 20 to be directed toward the work W such as to irradiatethe work W. The configuration of one or more embodiments is alsoprovided with the imaging lens 30A that causes linearly polarized light(the reference light component and the measurement light component ofthe first light) emitted from the second face 20 b of the polarizingbeam splitter 20 to be imaged on the first camera 33A and with theimaging lens 30B that causes linearly polarized light (the referencelight component and the measurement light component of the second light)emitted from the first face 20 a of the polarizing beam splitter 20 tobe imaged on the second camera 33B.

Compared with the conventional configuration that does not use theobject lens and the like, this configuration increases a change in theluminance value even at an identical reconstruction position having anidentical relative distance (reconstruction distance) from the optimumfocusing position as shown in the table of FIG. 21 in the process ofstep S5 described above (the process of determining the optimum focusingposition with regard to the specific area V) and in the process of stepS8 described above (the process of determining the optimum focusingposition with regard to each of the coordinate positions in themeasurement area on the work W).

As a result, this configuration facilitates the specification of theoptimum focusing position and is unlikely to be affected by the noise orthe like and thereby achieves improvement of the measurement accuracy.

The present disclosure is not limited to the description of the aboveembodiments but may be implemented, for example, by configurationsdescribed below. The present disclosure may also be naturallyimplemented by applications and modifications other than thoseillustrated below.

(a) The work W as the object to be measured or the measurement object isnot limited to the wafer substrate 100 illustrated in the aboveembodiments. For example, the work W (measurement object) may be aprinted circuit board with solder paste printed thereon.

According to a modified configuration, the three-dimensional measurementdevice 1 may be provided in a bump inspection device or a solderprinting inspection device that is equipped with an inspection unitconfigured to perform an inspection for the good/poor quality of a bumpor solder paste as a measurement target according to preset criteria ofgood/poor quality judgment.

(b) The embodiments described above employ the phase shift method usinga plurality of image data as the method of reconstruction frominterference fringe images (i.e., the method of obtaining the complexamplitude data). This is, however, not essential, but another method maybe employed. For example, a Fourier transform method using one imagedata may be employed.

The method of reconstruction is also not limited to the method ofreconstruction using the complex amplitude data, but anotherreconstruction method may be employed.

The calculation of light propagation is also not limited to theconvolution method illustrated in the above embodiments, but anothermethod, for example, an angular spectrum method, may be employed.

(c) The configuration of the interference optical system (thepredetermined optical system) is not limited to the configurationdescribed in the above embodiments. For example, the above embodimentsemploy the optical configuration of the Michelson interferometer for theinterference optical system. This is, however, not essential. Theinterference optical system may employ another optical configurationthat splits incident light into reference light and measurement lightand performs measurement of the work W, for example, the opticalconfiguration of a Mach-Zehnder interferometer or a Fizeauinterferometer.

(d) The above embodiments are configured to perform measurement of thework W by using two different types of lights having differentwavelengths. This is, however, not essential. A modification may beconfigured to perform measurement of the work W by using only one typeof light.

The configuration of using the two different types of lights havingdifferent wavelengths is not limited to the configuration described inthe above embodiments. Like the conventional three-dimensionalmeasurement device, a modified configuration may cause a combined lightof a first wavelength light and a second wavelength light to enter aninterference optical system, use a predetermined optical separation unit(for example, a dichroic mirror) to separate an interference lightemitted from the interference optical system by wavelength separation toobtain an interference light with regard to the first wavelength lightand an interference light with regard to the second wavelength light,and perform measurement of the work W, based on interference fringeimages obtained by individually imaging the interference lights withregard to the respective wavelength lights.

Another modified configuration may use three or more different types oflights of different wavelengths to perform measurement of the work W bycombining the configuration of causing a combined light of two differenttypes of lights of different wavelengths emitted from two light sourcesto enter an interference optical system, using an optical separationunit to separate the interference light emitted from the interferenceoptical system by wavelength separation and individually imaginginterference lights with regard to the respective lights of thedifferent wavelengths, with the configuration of the above embodiments.

(e) The configuration of the projection optical systems 2A and 2B is notlimited to the configuration described in the above embodiments. Forexample, the above embodiments illustrate the configuration that causesthe light having the wavelength λ₁=1500 nm to be radiated from the firstprojection optical system 2A and causes the light having the wavelengthλ₂=1503 nm to be radiated from the second projection optical system 2B.The wavelengths of the respective lights are, however, not limited tothis example. In this regard, however, a wavelength difference betweentwo lights may be reduced, in order to expand the measurement range.

The light emitters 11A and 11B according to the above embodiments areconfigured to employ the laser light sources and emit the laser lights.This is, however, not essential, but another configuration may beemployed. The configuration employable is required to emit light havinga high coherence (high coherent light) such as to make at leastinterference.

For example, a modified configuration may enhance the coherence and emitthe coherent light by combining an incoherent light source such as anLED light source with a bandpass filter or a special filter that allowsfor transmission of only a specific wavelength.

(f) The above embodiments are configured to obtain the four differentinterference fringe images having the phases differing by 90 degreeseach, with regard to each of the first light and the second light. Thenumber of phase shifts and the amount of phase shift are, however, notlimited to those of the above embodiments. For example, a modificationmay be configured to obtain three different interference fringe imageshaving phases differing by 120 degrees (or 90 degrees) each and toperform measurement of the work W.

(g) The above embodiments employ the polarizing plates 32A and 32Bconfigured to change the direction of the transmission axis, as thephase shift unit. The configuration of the phase shift unit is, however,not limited to the embodiments.

For example, one employable configuration may move the reference plane25 along an optical axis by a piezoelectric element or the like, so asto physically change the optical path length.

This employable configuration or the configuration of the aboveembodiments, however, takes a certain time period to obtain all theinterference fringe images required for measurement. This increases themeasurement time and is likely to lower the measurement accuracy, due tothe influence of the fluctuation of the air, the vibration or the like.

According to a modified configuration, for example, the first imagingsystem 4A may be provided with a spectroscopic unit (for example, aprism) configured to split the combined light (the reference lightcomponent and the measurement light component) with regard to the firstlight transmitted through the quarter-wave plate 31A into four lightsand may also be provided with a filter unit configured to providedifferent phase differences to the four lights emitted from thespectroscopic unit, in place of the first polarizing plate 32A, as thephase shift unit. The modified configuration may use the first camera33A (or a plurality of cameras) to simultaneously take images of thefour lights transmitted through the filter unit. A similar configurationmay also be applied for the second imaging system 4B.

A special camera equipped with polarizing plates of different angles forrespective pixels of an imaging element may be used, instead of theabove configuration.

For example, as shown in FIG. 13 , the camera used may include a lensunit 402 that includes microlenses 401 arranged in a matrix to enhancethe light condensing efficiencies of respective pixels; a filter unit404 that includes polarizing plates 403 arranged in a matrix to allowfor selective transmission of a predetermined component of the lightsemitted from the respective microlenses 401 and that serves as thefilter unit; and an imaging element 406 that includes a plurality ofpixels 405 arranged in a matrix to respectively receive the lightstransmitted through the respective polarizing plates 403.

The polarizing plates 403 constituting the filter unit 404 are comprisedof four different types of polarizing plates 403 a, 403 b, 403 c and 403d that have different directions of transmission axis by 45 degreeseach. More specifically, the polarizing plates 403 are comprised offirst polarizing plates 403 a having the direction of the transmissionaxis of 0 degree, second polarizing plates 403 b having the direction ofthe transmission axis of 45 degrees, third polarizing plates 403 chaving the direction of the transmission axis of 90 degrees, and fourthpolarizing plates 403 d having the direction of the transmission axis of135 degrees.

The filter unit 404 is configured such that sets of polarizing plates(shown by a thick frame portion in FIG. 13 ) where four different typesof polarizing plates 403 a, 403 b, 403 c and 403 d are arrayed in apredetermined sequence in a two by two matrix, are arranged in a matrix.

Using such a camera allows for calculation of the phase shift in fouradjacent pixels. Instead of using the adjacent pixels, a modified methodmay decompose an original image into images of 0 degree, 45 degrees, 90degrees and 135 degrees, generate four images by enlarging the size ofthe decomposed images to the size of the original image, and performcalculation of the phase shift with regard to each pixel. A methodemployed for the enlargement may be an interpolation technique by abilinear method or a bicubic method, but this method is not essential.

This configuration enables all the interference fringe images requiredfor measurement to be obtained simultaneously. More specifically, thisconfiguration enables a total of eight different interference fringeimages with regard to the two different types of lights to be obtainedsimultaneously. As a result, this configuration improves the measurementaccuracy and significantly shortens the total imaging time so as toremarkably enhance the measurement efficiency.

(h) The above embodiments are configured to obtain the complex amplitudedata and the like at every measurement range interval in heightmeasurement in the process of determining the position of the work W inthe z direction (the optimum focusing position with regard to thespecific area V). This configuration is, however, not essential. Forexample, a modified configuration may obtain the complex amplitude dataand the like at every focusing range interval.

(i) The above embodiments are configured to perform thethree-dimensional measurement at step S10, based on the complexamplitude data of the entire measurement area obtained at step S6. Amodification may be configured to obtain an intensity image of theentire measurement area and perform two-dimensional measurement, basedon the complex amplitude data of the entire measurement area obtained atstep S6, in addition to the three-dimensional measurement.

In the case of obtaining the intensity image of the entire measurementarea, different data may be used according to a difference in thefocusing position in the direction of the optical axis at each of thecoordinate positions in the measurement area. For example, data at afirst position in the direction of the optical axis may be used withregard to a first area included in the measurement area, and data at asecond position in the direction of the optical axis may be used withregard to a second area included in the measurement area. This enables afocused intensity image to be obtained over the entire measurement areaeven in the case where there is a height difference in the measurementarea, for example, due to a warp or an inclination of the object to bemeasured or the measurement object.

A procedure of the two-dimensional measurement may compare positionaldeviations Δx and Δy, an outer diameter D, an area S or the like of abump 101 (shown in FIG. 10 ) that is a measurement target, with areference value set in advance, based on the result of the measurementand may perform two-dimensional inspection to determine the good/poorquality of the bump 101, based on the determination of whether theresult of the comparison is within an allowable range.

In the case of performing both the two-dimensional measurement and thethree-dimensional measurement at step S10, a procedure may perform acomprehensive inspection as a combination of multiple differentmeasurements, for example, by specifying a location where the bump 101as the measurement target is present, based on the result of thetwo-dimensional measurement (two-dimensional inspection) and thenperforming the three-dimensional measurement or by mapping the intensityimage to three-dimensional data obtained by the three-dimensionalmeasurement.

(j) In the configuration of the above embodiments, the objective lens 21is placed between the polarizing beam splitter 20 (the third face 20 c)and the quarter-wave plate 23, and the objective lens 22 is placedbetween the polarizing beam splitter 20 (the fourth face 20 d) and thequarter-wave plate 24. The arrangement of the objective lenses 21 and 22is, however, not limited to this configuration.

The configuration of the above embodiments may be replaced by, forexample, a configuration that the objective lens 21 is placed betweenthe quarter-wave plate 23 and the reference plane 25. Similarly, theconfiguration of the above embodiments may be replaced by, for example,a configuration that the objective lens 22 is placed between thequarter-wave plate 24 and the mounting portion 26 (the work W).

In the configuration of the above embodiments, the imaging lens 30A isplaced between the second non-polarizing beam splitter 13B and thequarter-wave plate 31A, and the imaging lens 30B is placed between thefirst non-polarizing beam splitter 13A and the quarter-wave plate 31B.The arrangement of the imaging lenses 30A and 30B is, however, notlimited to this configuration.

The configuration of the above embodiments may be replaced by, forexample, a configuration that the imaging lens 30A is placed between thequarter-wave plate 31A and the first polarizing plate 32A or between thefirst polarizing plate 32A and the first camera 33A. Similarly, theconfiguration of the above embodiments may be replaced by, for example,a configuration that the imaging lens 30B is placed between thequarter-wave plate 31B and the second polarizing plate 32B or betweenthe second polarizing plate 32B and the second camera 33B.

(k) The above embodiments are configured to specify the optimum focusingposition with regard to the specific area V that is set in advance as apart in the measurement area on the work W, i.e., the position of thework W in the z direction, to subsequently obtain the complex amplitudedata and the intensity image data at a plurality of positions in the zdirection with regard to the entire measurement area, based on thespecified position, and to perform the measurement.

This configuration is, however, not essential. A modified configurationmay omit the process of specifying the optimum focusing position withregard to the specific area V but may directly obtain the complexamplitude data and the intensity image data at a plurality of positionsin the z direction with regard to each of the coordinate positions inthe entire measurement area on the work W, on the basis of the deviceorigin of the three-dimensional measurement device 1, and perform themeasurement.

The following describes one or more embodiments of this configuration indetail with reference to FIG. 14 . FIG. 14 is a flowchart showing theflow of a measurement process according to one or more embodiments. Withregard to overlapping portions with those of the above embodiments, thedetailed description is omitted with using like names of members andlike reference signs. The following mainly describes different portionsfrom those of the above embodiments.

At first step T1, the control device 5 performs a process of obtaininginterference fringe images with regard to a predetermined measurementarea on the work W. More specifically, the control device 5 obtains allthe image data required for measurement with regard to the predeterminedmeasurement area on the work W (a total of eight interference fringeimages consisting of four interference fringe images of different phaseswith regard to the first light and four interference fringe images ofdifferent phases with regard to the second light). The processing ofstep T1 is similar to the processing of step S1 described in the aboveembodiments and is thus not described in detail.

At subsequent step T2, the control device 5 performs a process ofobtaining complex amplitude data of light on the imaging element33Aa-face or on the imaging element 33Ba-face.

The control device 5 obtains complex amplitude data Eo(x,y) of light onthe imaging element 33Aa-face or on the imaging element 33Ba-face withregard to each of the first light and the second light, based on thefour interference fringe images with regard to the first light and thefour interference fringe images with regard to the second light storedin the image data storage device 54. The processing of step T2 issimilar to the processing of step S2 described in the above embodimentsand is thus not described in detail.

At subsequent step T3, the control device 5 performs a process ofobtaining complex amplitude data at a plurality of positions in the zdirection, with regard to each of coordinate positions in apredetermined measurement area and in a predetermined reference area onthe work W, at every predetermined measurement range interval within apredetermined range in the z direction where a predetermined measurementtarget on the work W (for example, a bump 101 on a wafer substrate 100)is likely to be present, on the basis of the device origin that is thestandard of height measurement in the three-dimensional measurementdevice 1. The method of obtaining the complex amplitude data at theplurality of positions in the z direction is similar to the methoddescribed in the above embodiments and is thus not described in detail.

The “reference area” denotes an area including a reference plane forheight measurement of the predetermined measurement target. For example,when the work W is a wafer substrate 100 as shown in FIG. 8 , thereference area is an area including a substrate upper face (or an upperface of a pattern portion 102) that is likely to serve as a referenceplane for height measurement of a predetermined bump 101 as ameasurement target.

At subsequent step T4, the control device 5 performs a process ofobtaining intensity image (luminance image) data at a plurality ofpositions in the z direction with regard to each of the coordinatepositions in the predetermined measurement area and in the predeterminedreference area on the work W, based on the complex amplitude dataobtained at step T3 described above. Accordingly, the function ofperforming the series of processes of steps T3 and T4 described aboveconfigures the image data obtaining unit according to one or moreembodiments. The method of obtaining the intensity image data from thecomplex amplitude data is similar to the method described in the aboveembodiments and is thus not described in detail.

At subsequent step T5, the control device 5 performs a process ofdetermining the optimum focusing position (the focusing position in thedirection of the optical axis) with regard to each of the coordinatepositions in the predetermined measurement area and in the predeterminedreference area on the work W, based on the intensity image data at theplurality of positions in the z direction obtained at step T4 describedabove. The function of performing this process of step T5 configures thefocusing position determination unit according to one or moreembodiments. The method of determining the optimum focusing positionfrom the intensity image data at the plurality of positions in the zdirection is similar to the method described in the above embodimentsand is thus not described in detail.

At subsequent step T6, the control device 5 performs a process ofspecifying an order corresponding to the optimum focusing position withregard to each of the coordinate positions in the predeterminedmeasurement area and in the predetermined reference area on the work Wdetermined at step T5, as an order of a measurement range with regard toeach of the coordinate positions. The function of performing thisprocess of step T6 configures the order specification unit according toone or more embodiments. The method of specifying the order of themeasurement range is similar to the method described in the aboveembodiments and is thus not described in detail.

At subsequent step T7, the control device 5 performs a three-dimensionalmeasurement process. The function of performing this process of step T7configures the three-dimensional measurement unit according to one ormore embodiments.

Like the three-dimensional measurement process of the above embodiments,the control device 5 first calculates a phase ϕ(ξ,η) of the measurementlight and an amplitude A(ξ,η) of the measurement light from the complexamplitude data Eo(ξ,η) at the optimum focusing position with regard toeach of the coordinate positions in the measurement area and in thepredetermined reference area determined at step T5. The function ofperforming the series of reconstruction process to calculate the phaseϕ(ξ,η) that is the phase information of the measurement light configuresthe phase information obtaining unit according to one or moreembodiments.

The control device 5 subsequently performs a phase-height conversionprocess and calculates height information z(ξ,η) in the measurementrange that shows the surface roughness or the concavo-convexconfiguration on the surface of the work W (the measurement area and thereference area) in a three-dimensional manner.

The control device 5 then obtains true height data (actual height) 7 bwith regard to each coordinate position, based on the height informationz(ξ,η) in the measurement range calculated as described above and theorder of the measurement range with regard to the coordinate positionspecified at step T6.

One or more embodiments are configured to calculate an average value ofheights in reference areas (for example, a plurality of positions on asubstrate upper face or upper faces of a plurality of pattern portions102) present in the periphery of each measurement target (for example,one bump 101) and to subsequently calculate the height of themeasurement target based on the calculated average value.

A modification may be configured to create a height map of a referencearea (for example, a substrate upper face or an upper face of a patternportion 102) in a predetermined range on a work W (for example, a wafersubstrate 100) including a plurality of measurement targets (forexample, a plurality of bumps 101) and to subtract an absolute height ofthe reference area at the position of a predetermined measurement targetfrom an absolute height of the predetermined measurement target, so asto calculate the height of the measurement target relative to areference plane (the reference area).

This configuration allows for the more appropriate height measurement ofthe measurement target even in the case of an inclination of thereference plane or the measurement area due to, for example, a warp ofthe work W or inclination of the mounting portion 26 (mounting plane).

(l) The above embodiments are configured to obtain the intensity imagedata at a plurality of positions in the z direction at every interval ofone period of the measurement range and determine the focusing state.This configuration may be replaced by a configuration of obtainingintensity image data at a plurality of positions in the z direction atevery interval of n periods of the measurement range (where n is anatural number of not less than 2) and determine the focusing state.

Like a concrete example shown in FIG. 12 , for example, a modifiedconfiguration may obtain intensity image data at a plurality ofpositions in the z direction at every interval of two periods of themeasurement range and determine the focusing state.

In a “Case 1” shown in FIG. 12 , among intensity image datareconstructed at height positions H₃, H₁, H⁻¹, and H⁻³ (reconstructedimages [1] to [4]) with regard to a predetermined coordinate position,the intensity image data reconstructed at the height position H₃(reconstructed image [1]) has a maximum luminance value of “135”.Accordingly, the height position H₃ is specified as the optimum focusingposition with regard to this coordinate position.

Similarly, in a case “2” shown in FIG. 12 , among intensity image datareconstructed at height positions H₃, H₁, H⁻¹, and H⁻³ (reconstructedimages [1] to [4]) with regard to a predetermined coordinate position,the intensity image data reconstructed at the height position H₁(reconstructed image [2]) has a maximum luminance value of “128”.Accordingly, the height position H₁ is specified as the optimum focusingposition with regard to this coordinate position.

A modification may be configured to obtain interpolation data at heightpositions H₂, H₀, and H⁻², based on the intensity image datareconstructed at the height positions H₃, H₁, H⁻¹, and H⁻³ (thereconstructed images [1] to [4]) and specify the optimum focusingposition, based on the interpolation data and the reconstructedintensity image data.

Another modification may be configured to obtain intensity image data ata plurality of positions in the z direction at every reconstructioninterval that is shorter than one period of the measurement range anddetermine the focusing state (reconstruction interval dz<measurementrange interval R).

(m) The above embodiments are configured to obtain the intensity imagedata at a plurality of positions in the z direction with regard to eachof the coordinate positions in the measurement area, determine thefocusing state, and perform measurement. This configuration is, however,not essential. A modification may be configured to obtain intensityimage data at one predetermined position in the z direction with regardto each of the coordinate positions in the measurement area, determinethe focusing state (the focusing determination unit), and, when theintensity image data has a predetermined focusing state satisfying apredetermined condition (for example, when the intensity image data hasa luminance of not lower than a predetermined reference value), performthree-dimensional measurement with regard to the coordinate position,based on phase information of light obtained from complex amplitude dataat the predetermined position in the z direction and an ordercorresponding to the predetermined position in the z direction.

(n) A modification may be configured to add projection lenses to theconfiguration of the above embodiments. For example, as shown in FIG. 15, a projection lens 500A may be provided between the first lightisolator 12A and the first non-polarizing beam splitter 13A in the firstprojection optical system 2A, and a projection lens 500B may be providedbetween the second light isolator 12B and the second non-polarizing beamsplitter 13B in the second projection optical system 2B.

In the configuration provided with the objective lenses 21 and 22 likethe above embodiments, the light (measurement light) which the work W isirradiated with is gathered at one point (in a narrow range). This islikely to narrow a measurement area that is measurable by onemeasurement.

In the above modified configuration, on the other hand, the projectionlenses 500A and 500B serve to collect the lights emitted from the lightemitters 11A and 11B toward the objective lenses 21 and 22. This enablesa wider range of the work W to be irradiated with uniform parallel lightand thereby enables a wider range to be measured more uniformly by onemeasurement.

As a result, this further improves the measurement accuracy and furtherenhances the measurement efficiency.

The arrangement of the projection lenses 500A and 500B is, however, notlimited to the above configuration. For example, the above configurationmay be replaced by a configuration that the projection lens 500A isplaced between the first light emitter 11A and the first light isolator12A or is placed between the first non-polarizing beam splitter 13A andthe polarizing beam splitter 20 (the first face 20 a).

Similarly, the above configuration may be replaced by a configurationthat the projection lens 500B is placed between the second light emitter11B and the second light isolator 12B or is placed between the secondnon-polarizing beam splitter 13B and the polarizing beam splitter 20(the second face 20 b).

(o) The objective lenses 21 and 22 used may be those having a numericalaperture NA satisfying Expression (01) given below, although thiscondition is not specifically referred to in the above embodiments:

NA>a/√((dz)² +a ²)  (01)

where a denotes a pixel size and dz denotes a reconstruction interval.

For example, in the case where it is required to specify a deviation ofthe reconstruction position from the optimum focusing position under theconditions of the pixel size a=2 [μm] and the reconstruction intervaldz=3 [μm], the objective lenses 21 and 22 having the numerical apertureNA>0.5547 may be used.

In this regard, however, the reconstruction intervals dz is not lessthan 0 and does not exceed the measurement range interval R (0≤dz≤R) inone or more embodiments. The numerical aperture NA may be larger as longas possible. Unless a special technique such as liquid immersion isemployed, however, the upper limit of the numerical aperture NA is equalto 1 (refer to Expression (2) given above in the case of a refractiveindex n=1). Accordingly, the numerical aperture NA is not greater than 1(NA 1) in one or more embodiments.

In the case of using the objective lenses 21 and 22 having a relativelysmall numerical aperture NA, even a relatively large reconstructioninterval dz (relative distance from the optimum focusing position) islikely to reduce the degree of blurring of a measurement point and makesit difficult to specify the optimum focusing position.

In the case of using the objective lenses 21 and 22 having a relativelylarge numerical aperture NA as described above, on the other hand,reflected light that is reflected in a wide range such as a top portionof the bump 101 is more readily received by the objective lens 22. Evena small reconstruction interval dz is likely to increase the degree ofblurring of the measurement point and makes it easier to specify theoptimum focusing position.

Although the disclosure has been described with respect to only alimited number of embodiments, those skilled in the art, having benefitof this disclosure, will appreciate that various other embodiments maybe devised without departing from the scope of the present invention.Accordingly, the scope of the invention should be limited only by theattached claims.

REFERENCE SIGNS LIST

-   -   1 . . . three-dimensional measurement device, 2A . . . first        projection optical system, 2B . . . second projection optical        system, 3 . . . interference optical system, 4A . . . first        imaging system, 4B . . . second imaging system, 5 . . . control        device, 11A . . . first light emitter, 11B . . . second light        emitter, 12A . . . first light isolator, 12B . . . second light        isolator, 13A . . . first non-polarizing beam splitter, 13B . .        . second non-polarizing beam splitter, 20 . . . polarizing beam        splitter, 20 a . . . first face, 20 c . . . third face, 20 b . .        . second face, 20 d . . . fourth face, 21, 22 . . . objective        lenses, 23, 24 . . . quarter-wave plates, 25 . . . reference        plane, 26 . . . mounting portion, 30A, 30B . . . imaging lenses,        31A . . . quarter-wave plate, 31B . . . quarter-wave plate, 32A        . . . first polarizing plate, 32B . . . second polarizing plate,        33A . . . first camera, 33B . . . second camera, 33Aa, 33Ba . .        . imaging elements, 100 . . . wafer substrate, 101 . . . bump,        102 . . . pattern portion, R . . . measurement range interval, V        . . . specific area, W . . . work

What is claimed is:
 1. A three-dimensional measurement device,comprising: an irradiator that emits a predetermined light; an opticalsystem that splits the predetermined light entering from the irradiatorinto two lights, irradiates a measurement object with one of the twolights as a measurement light and irradiates a reference plane withanother of the two lights as a reference light, and combines themeasurement light and the reference light with each other and emits acombined light; an imaging device that takes an image of the combinedlight emitted from the optical system and obtains an interference fringeimage; an objective lens for the measurement light that directs themeasurement light toward the measurement object; an objective lens forthe reference light that directs the reference light toward thereference plane; an imaging lens that forms an image of the combinedlight on the imaging device; and a control device that executesthree-dimensional measurement of a measurement area on the measurementobject based on the interference fringe image, wherein the controldevice is configured to: obtain, by reconstruction, intensity image dataat a predetermined position along an optical axis for each coordinate inthe measurement area, based on the interference fringe image of themeasurement area, obtain, by reconstruction, phase information of lightat the predetermined position along the optical axis for each coordinatein the measurement area, based on the interference fringe image of themeasurement area, determine whether the intensity image data is in afocusing state that satisfies a predetermined condition, based on theintensity image data at the predetermined position along the opticalaxis with respect to a predetermined coordinate in the measurement area,after determining that the intensity image data at the predeterminedposition along the optical axis is in the focusing state with respect tothe predetermined coordinate, specify an order corresponding to thepredetermined position along the optical axis, among orders set at apredetermined measurement range interval along the optical axis, as anorder of the predetermined coordinate, and execute three-dimensionalmeasurement with respect to the predetermined coordinate, based on thephase information of the predetermined coordinate and the order of thepredetermined coordinate, and the objective lens has a numericalaperture NA that satisfies an expression given below:NA>a/√((dz)² +a ²), where a denotes a pixel size and dz denotes areconstruction interval.
 2. A three-dimensional measurement device,comprising: an irradiator that emits a predetermined light; an opticalsystem that splits the predetermined light entering from the irradiatorinto two lights, irradiates a measurement object with one of the twolights as a measurement light and irradiates a reference plane withanother of the two lights as a reference light, and combines themeasurement light and the reference light with each other and emits acombined light; an imaging device that takes an image of the combinedlight emitted from the optical system and obtains an interference fringeimage; an objective lens for the measurement light that directs themeasurement light toward the measurement object; an objective lens forthe reference light that directs the reference light toward thereference plane; an imaging lens that forms an image of the combinedlight on the imaging device; and a control device that executesthree-dimensional measurement of a measurement area on the measurementobject based on the interference fringe image, wherein the controldevice is configured to: obtain, by reconstruction, a plurality ofpieces of intensity image data at a predetermined interval at leastwithin a predetermined range along an optical axis, each piece ofintensity image data being at a predetermined position along the opticalaxis for each coordinate in the measurement area, based on theinterference fringe image of the measurement area, determine a focusingposition along the optical axis for a predetermined coordinate in themeasurement area, based on the plurality of pieces of intensity imagedata with respect to the predetermined coordinate, specify an ordercorresponding to the focusing position along the optical axis for thepredetermined coordinate, among orders set at a predeterminedmeasurement range interval along the optical axis, as an order of thepredetermined coordinate, obtain, by reconstruction, phase informationof light at the predetermined position along the optical axis for eachcoordinate in the measurement area, based on the interference fringeimage of the measurement area, and execute three-dimensional measurementwith respect to the predetermined coordinate, based on the phaseinformation of the predetermined coordinate and the order of thepredetermined coordinate, and the objective lens has a numericalaperture NA that satisfies an expression given below:NA>a/√((dz)² +a ²), where a denotes a pixel size and dz denotes areconstruction interval.
 3. A three-dimensional measurement device,comprising: an irradiator that emits a predetermined light; an opticalsystem that splits the predetermined light entering from the irradiatorinto two lights, irradiates a measurement object with one of the twolights as a measurement light and irradiates a reference plane withanother of the two lights as a reference light, and combines themeasurement light and the reference light with each other and emits acombined light; an imaging device that takes an image of the combinedlight emitted from the optical system and obtains an interference fringeimage; an objective lens for the measurement light that directs themeasurement light toward the measurement object; an objective lens forthe reference light that directs the reference light toward thereference plane; an imaging lens that forms an image of the combinedlight on the imaging device; and a control device that executesthree-dimensional measurement of a measurement area on the measurementobject based on the interference fringe image, wherein the controldevice is configured to: obtain, by reconstruction, a plurality ofpieces of intensity image data at a predetermined interval at leastwithin a first range along an optical axis, each piece of intensityimage data being at a predetermined position along the optical axiswithin a specific area set in advance in the measurement area, based onthe interference fringe image, determine a first focusing position alongthe optical axis within the specific area, based on the plurality ofpieces of intensity image data with respect to the specific area,obtain, by reconstruction, a plurality of pieces of intensity image dataat a predetermined interval at least within a second range along theoptical axis set based on the first focusing position, each piece ofintensity image data being at a predetermined position along the opticalaxis for each coordinate in the measurement area, based on theinterference fringe image of the measurement area, determine a secondfocusing position along the optical axis for a predetermined coordinatein the measurement area, based on the plurality of pieces of intensityimage data with respect to the predetermined coordinate, specify anorder corresponding to the second focusing position, among orders set ata predetermined measurement range interval along the optical axis, as anorder of the predetermined coordinate, obtain, by reconstruction, phaseinformation of light at the predetermined position along the opticalaxis for each coordinate in the measurement area, based on theinterference fringe image of the measurement area, and executethree-dimensional measurement with respect to the predeterminedcoordinate, based on the phase information of the predeterminedcoordinate and the order of the predetermined coordinate, and theobjective lens has a numerical aperture NA that satisfies an expressiongiven below:NA>a/√((dz)² +a ²), where a denotes a pixel size and dz denotes areconstruction interval.
 4. The three-dimensional measurement deviceaccording to claim 1, wherein the irradiator comprises: a first lightemitter that emits a first light including a polarized light of a firstwavelength and entering the optical system; a second light emitter thatemits a second light including a polarized light of a second wavelengthand entering the optical system; a projection lens for the first lightthat is placed between the optical system and the first light emitterand collects the first light directed onto the objective lens; and aprojection lens for the second light that is placed between the opticalsystem and the second light emitter and collects the second lightdirected onto the objective lens, the imaging device includes: a firstimaging device that takes an image of the combined light emitted fromthe optical system once the first light enters the optical system; and asecond imaging device that takes an image of the combined light emittedfrom the optical system once the second light enters the optical system,and the imaging lens includes: an imaging lens for first imaging thatforms an image of the combined light of the first light on the firstimaging device; and an imaging lens for second imaging that forms animage of the combined light of the second light on the second imagingdevice.
 5. The three-dimensional measurement device according to claim1, wherein the measurement object is a wafer substrate with a bumpformed on the wafer substrate.
 6. The three-dimensional measurementdevice according to claim 2, wherein the measurement object is a wafersubstrate with a bump formed on the wafer substrate.
 7. Thethree-dimensional measurement device according to claim 3, wherein themeasurement object is a wafer substrate with a bump formed on the wafersubstrate.
 8. The three-dimensional measurement device according toclaim 4, wherein the measurement object is a wafer substrate with a bumpformed on the wafer substrate.